1A10 - Basic Units

Dubious Clocks Two large "clocks" without numbers mounted on the same vertical board. The clocks coincide at zero on each revolution, but differ in their readings elsewhere around the circle. The difference is subtle enough to encourage doubt as to which is "correct." Shows that timing devices can be useful for some measurements but worthless for others.

1A20 - Error and Accuracy

Calipers and Micrometers (1A20.41) Vernier and digital calipers, and micrometers.

1A30 - Coordinate Systems

Chalkboard Globe (1A30.40) A large globe surfaced with a black material that can be written on with chalk. Can be used to draw and discuss polar coordinates.

Acrylic Globe Clear plastic globe has lines of latitude and longitude drawn on it for discussion of polar coordinate systems.

1A40 - Vectors

Vector in Coordinate Frame (1A40.10) A three dimensional stick-and-ball coordinate frame has a vector arrow emerging from the origin that can be adjusted to any angle within the frame.

Sum Vector (1A40.31) A pair of acrylic vector arrows make up two sides of a parallelogram, with a tape measure "vector" extending diagonally across the parallelogram to represent the sum of the vectors. Change the angle between the vectors and the length of the sum vector changes in accordance with the parallelogram rule.

1A50 - Math Topics

Radian Disc (1A50.10) A large disc marked off in radians, with a flexible strip of length r to show the derivation of the unit.

1A60 - Scaling

"Powers of Ten" (1977) (1A60.10) A ten minute video which uses the notion of powers of ten to compare the relative sizes of objects in the universe, from clusters of galaxies to individual protons.

1C10 - Velocity

1C20 - Uniform Acceleration

Guinea and Feather (1C20.10) Two transparent tubes contain paper and an aluminum disc. Free fall times for the discs are compared when the tubes are at atmospheric pressure and when they are evacuated.

1C30 - Measuring g

Timed Free Fall (1C30.10) An electromagnet drops a ball from heights of 1 and 2 meters. A clock starts upon release and stops when the ball strikes a cup at the bottom.

1D10 - Displacement in Two Dimensions

1D15 - Velocity, Position, and Acceleration

Sliding Weights on Right Triangle (1D15.41) A wire frame triangle is positioned so that beads sliding down the wires traverse each side in the same time.

1D40 - Motion of the Center of Mass

1D50 - Central Forces

Ball on a String (1D50.10) A ball on string is swung around to show the basics of circular motion. Run the string through a handheld tube, start the ball spinning with all the string out, and then pull the string through the tube to decrease the radius of the ball's rotation. The ball will gain angular velocity to conserve angular momentum.

Conical Pendulum (1D50.25) String and weight pendulum swung in a circle.

Rotor (Carnival Ride Model) (1D50.30) A horizontal disc rotating at about 2 rev/s has a small section of a vertical wall at the edge. At sufficient speed, the centripetal force will keep a small object pressed against the wall without falling down.

Greek Waiter’s Tray A small circular plastic plate hangs from three strings tied symmetrically to its edge. The three strings are tied together at the top so that the plate hangs horizontally beneath them. A small glass of water is placed at the center of the plate. The plate can now be swung around in any direction, and the surface of the water in the glass will always stay parallel to the plate. The plate can also be swung overhead without spilling a drop.

Arrow Disc A wooden disc with an arrow showing one direction of rotation and an arrow along the axis showing the direction of the angular momentum vector for that spin direction.

1D52 - Deformation by Central Forces

Flattening Earth (1D52.10) A flexible hoop becomes oblate when rotated.

Rotating Rubber Wheel (1D52.61) A flat spoked rubber wheel is rotated at high speed with a motor and expands outward slightly.

1D55 - Centrifugal Escape

Circular Track with Gap (1D55.10) A ball bearing is rolled around the inside of a circular track. Students predict which path the ball will take when it reaches the opening. Uses the document camera.

Rotating Disk with Erasers (1D55.30) A horizontal rotating disc with a smooth surface. Chalk board erasers with various surfaces are placed on the disc, which is rotated slowly until the erasers slide off; how long this takes depends on rotation speed, distance from the center, and eraser surface. A weight attached to the rotation axis by a rubber band shows qualitatively how the centripetal force increases with rotation speed.

1D60 - Projectile Motion

Vertical Gun on Car (1D60.10) A vertical spring cannon is mounted to a cart running on a horizontal track. The cannon shoots a small ball vertically while the cart rolls horizontally. Since the cart travels at (nearly) constant velocity, the ball goes up and falls back into the cannon's top, staying directly above the cannon while in the air. Note: The Pasco apparatus can drift after firing. Be sure to check the aiming screws before repeating.

Drop and Shoot (1D60.20) A spring shoots one pool ball horizontally while simultaneously dropping another ball vertically. Both balls strike the floor simultaneously. Have a student volunteer catch the projected ball after the first bounce, while you catch the dropped ball.

Range Gun (1D60.40) A spring launcher shoots a wood ball at various angles and the distance traveled is marked. A large digital stopclock can be used to show times.

1E10 - Moving Reference Frames

Bulldozer on Plastic Sheet (1D or 2D) (1E10.10) One battery powered vehicle runs at a constant speed across the lecture table while a second runs across on a large sheet of plastic. Push or pull on the plastic sheet to show how velocities add or subtract. This can be done in one dimension or two; or used for frames of reference discussions.

"Frames of Reference" (1960) (1E10.20) An excellent film (black & white, 1960, approx 28 minutes) showing the apparent motion of objects with respect to various inertial and non-inertial frames of reference. Available on laserdisk or as an MPEG file from https://www.archive.org/details/frames_of_reference.

1E20 - Rotating Reference Frames

1F10 - Measuring Inertia

Inertia Balance (1F10.11) A platform is supported by two strips of spring steel, leaving it free to oscillate horizontally. Two blocks of similar appearance but different mass are placed on the platform; the lighter block oscillates at a higher frequency than the heavier block.

1F20 - Inertia of Rest

Inertia Block (Inertia Ball) (1F20.10) A heavy block is suspended between two loops of string. A slow and steady pull on the bottom loop will break the upper string, while a quick jerk will break only the lower string (due to the high inertia of the mass).

Eggs and Pizza Pan (1F20.35) Three raw eggs are propped up by cardboard cylinders which are standing on a round baking sheet. The baking sheet sits on three water filled beakers with a beaker directly under each egg. The pie sheet is knocked out by a broom (check on technique!), and the eggs drop straight down into the beakers of water.

1F30 - Inertia of Motion

1G10 - Force, Mass, and Acceleration

Heavy Cart with Spring or Spring Scale (1G10.15) A small wheeled cart is pulled along the table by a spring or spring scale with different forces to show different accelerations. The spring will give a smoother indication of a constant force (the scale bounces) but cannot give quantitative results. Weights may be added to vary the cart's mass.

Atwood's Machine (1G10.40) Two equal masses are attached to either end of a cord running over a pulley. Small additional weights can be added to one of the hanging masses to unbalance to weights and accelerate the system. A stopclock and a two meter stick can be used to show that acceleration is proportional to the unbalanced force.

1G20 - Accelerated Reference Frames

1H10 - Action and Reaction

Fan Car with Sail (1H10.20) A car with onboard fan and removeable "sail." Cart will not move at all with the sail perpendicular to the fan, but moves with the sail removed.

1H11 - Recoil

1J10 - Finding Center of Gravity

Irregular Objects (1J10.12) A piece of wood of irregular shape is hung on a metal pin from various points around its edge. Since the center of mass is directly beneath the point of support in each case, one can find it by using a plumb bob to draw vertical lines from two or more points of support - the lines intersect at the center of mass.

1J11 - Exceeding Center of Gravity

Leaning Tower of Pisa (1J11.10) A model tower leans on a slanted base and is stable until a cap is added to the top; that shifts the center of mass outside the base and the tower topples.

1J20 - Stable, Unstable, and Neutral Equilibrium

Stability of Geometric Shapes (1J20.11) A cone, cylinder, cube, and a sphere are used to discuss stability and equilibrium conditions. The sphere has neutral stability. The cone and cylinder are either in neutral, stable or unstable equilibria depending on how they rest on a surface.

Chair on a Pedestal (1J20.51) A chair with weighted legs balances on a pointed rod. Since the center of mass is below the point of support the chair is stable and may be knocked around without falling over.

Double Cone on Incline (1J20.70) Two rails fastened together at a small angle form an incline; a cylinder will roll down the incline but a double cone will roll "up" the incline because the widening of the rails allows it to lower its center of mass by moving in that direction.

1J30 - Resolution of Forces

Load on Removable Incline (1J30.10) A cart rests against a support block on an incline. A force can be applied parallel to the incline by a weight strung over a pulley, which is equal to the component of gravitational force in that direction. The support block can now be removed. Another weight is used to balance the normal force perpendicular to the incline; the incline can now also be removed. The cart will remain suspended in air.

Boom and Weight (1J30.40) A long boom is hinged at one end and supported by a cable at the other end. A large spring scale measures the force on the cable. Weights can be hung along the boom and the spring scale shows the resulting tension in the cable.

Force Board (1J30.50) Three strings are tied together to a common point, with their other ends passing over three pulleys and supporting three weights. Two different combinations of weights and string angles are available that will leave the common point in equilibrium under the three forces.

1J40 - Static Torque

Torque Bar (1J40.10) A T shaped rod with screw eyes spaced along its length. A weight is hooked to an eye and lifted off the table by twisting your wrists. The farther from your wrists the weight is, the harder it gets. Good for student participation.

Balancing Meter Stick (1J40.20) A meter stick which pivots at the center is supplied with masses which may be attached to the stick at various points to achieve different equilibria. Masses and distances are all simple 1:2:3 ratios for ease of calculation in class.

Hinge Board (1J40.21) A flat board with hooks at intervals is attached to the table by a hinge. Lift the board at different distances from the hinge with a spring scale, and observe the force required.

Torque Wheel (1J40.25) A wheel with coaxial pulleys of 5, 10, 15, and 20 cm to show static equilibrium of combinations of weights at various radii.

Bridge and Truck (1J40.40) A long board with position markings is supported at each end by a kitchen scale. A 10 lb. toy truck is rolled to different positions along the bridge while the forces at each end of the bridge are indicated by the scales.

1K10 - Dynamic Torque

Ladder Forces (1K10.20) A model ladder is positioned as though it were leaning against a wall, but is actually supported by three spring scales that provide the horizontal "wall" force and the horizontal and vertical "floor" forces needed to keep the ladder in equilibrium. A weight can be hung from various rungs of the ladder to vary the forces, which are read directly off the scales.

Large Spool with Wrapped Ribbon (Walking the Spool) (1K10.30) A large spool has a flat ribbon wrapped around its axle several times so that it will come off the bottom of the axle's shank as the spool rolls along the table. The spool will either roll clockwise, counter-clockwise, or slide without rolling, depending on the angle at which the ribbon is pulled.

Loaded Disc Rolling Uphill (1K10.50) A large disc has a lead weight hidden near one edge, so its center of mass is away from the center of the disc. If it is placed on an incline with the lead weight on the uphill side of the incline, it will roll uphill slightly because that lowers its center of mass.

1K20 - Friction

Four Surface Incline (1K20.10) A board is covered with strips of four different materials (teflon, sandpaper, bare wood, and rubber) that run down the length of the board. Identical brass blocks are placed at the end of each, and the end of the board near the blocks is slowly lifted up. As the angle increases, the blocks will slide down the strip in order of the different coefficients of friction.

Area Dependence of Friction (Plank and Weights with Spring Scale) (1K20.20) Pull a 2x12 plank along a level table at constant speed with a spring scale. Friction is approximately independent of which face the plank is sliding on (narrow or wide) and the plank's velocity. Add masses to increase frictional force.

Incline with Sliding Blocks (1K20.35) Blocks with different surfaces are placed on an incline, which is slowly raised until the block just begins to slide down. The tangent of the angle at that point equals the coefficient of static friction between the inclined board and the sliding block.

1K30 - Pressure

1L10 - Universal Gravitational Constant

Cavendish Balance Model (1L10.20) A large scale open model of the Cavendish balance.

Cavendish Balance Experiment and Video (1L10.30) Cavendish balance experiment which can measure the value of G to within 10% or less. Note: This experiment takes about 90 minutes to perform so most instructors use the video instead.

1L20 - Orbits

Conic Sections (1L20.40) A dissectable cone is cut several ways to give a circle, ellipse, parabola, and hyperbola.

Ellipse Drawing Board (1L20.51) An acrylic board with two adjustable pins and loops of string. Works well with the document camera.

1M10 - Work

Pile Driver with Nails (1M10.20) Five nails are just barely driven into a piece of wood. Masses slide down a rod and strike the heads of the nails one by one, driving them into the wood. The penetration depths of the nails are compared as an indicator of the energy released in four different configurations (two different heights and two masses) versus the control nail. Note: See also Pile Driver with Foam (1N10.30).

1M20 - Simple Machines

4:1 Ratio Pulleys Two pulleys with a 4:1 diameter ratio are bound together on a common axle. A weight on the large pulley is balanced by four times as much weight on the smaller.

1M40 - Conservation of Energy

Galileo's Pendulum (1M40.15) A pendulum swings in front of a white board with horizontal marks. The string strikes a stationary peg, which stops the top part of the string and shortens the pendulum, but the bob always rises close to the initial height.

Loop the Loop (1M40.20) A ball rolls down a straight section into a vertical circular loop and then into a uphill incline.

Energy Well Track (1M40.25) A ball rolls down an incline and up a shorter hill on the other side. If the ball's initial height is below a given mark, the ball will not have enough energy to roll up and over the hill, but will instead roll back and forth between the two inclines.

Triple Angle Track (1M40.33) Three inclined tracks each have the same downward slope, but different uphill angles on the other side. A ball rolled down each track in turn rolls up the other side to the same height in each case, despite the different slopes.

Ballistic Pendulum (1M40.41) A commercial ballistic pendulum apparatus that fires a ball bearing into a swinging arm catch mechanism.

Spring Jumper (1M40.67) A small jumping toy which shows that a spring may contain enough energy to launch itself into the air.

High Bounce Paradox (1M40.91) A raquetball that’s been cut in half. Invert the curve of the ball with your hand. When dropped, the ball will pop back upon colliding with the floor, releasing the stored energy you put in and making it bounce higher than the release height.

1M50 - Mechanical Power

Prony Brake (1M50.10) A student cranks on the handle for one minute against a constant frictional force. Knowing the drum circumference, the number of turns (and thus distance traveled), the force, and the time, horsepower can be calculated (about 0.25 hp max).

1N10 - Impulse and Thrust

Pile Driver with Foam (1N10.30) A pile driver drops a mass onto a plastic strip and cracks it, but not if a piece of foam is placed on the board. Same impulse, different force and time. Note: See also Pile Driver with Nails (1M10.20).

1N20 - Conservation of Linear Momentum

Reaction Carts Two rolling carts, one with a spring-loaded plunger, are tied together with a string. The string is burned, and the two carts are pushed apart by the spring and roll away with equal and opposite momentum. A large weight can be added to one cart to increase mass.

See-Saw Center of Mass (1N20.10) The Reaction Carts are balanced on a long see-saw board so that their center of mass is directly above the fulcrum. The board is horizontal and stable. When the string between the carts is burned, they spring apart with equal and opposite momenta. The center of mass remains above the fulcrum so the board remains balanced (until one cart strikes the end of the board). Most dramatic with different mass carts.

Radio Controlled Car on Rolling Board (Dog on Boat) (1N20.15) A radio controlled car sits on top of a short board that is mounted on wheels. Moving the car forward moves the board backward, and vice versa.

1N22 - Rockets

Water Rocket (1N22.20) A toy plastic water rocket uses pressurized air as a driving force. The amount of lift varies greatly with the selection of the exhaust: air exhaust will barely move the rocket (low mass transfer), but water exhaust can easily send the rocket to the ceiling.

CO2 Rotator (1N22.33) A CO2 cartridge is inserted in a cylinder at the end of a rotation arm. When the end of the cartridge is punctured, the escaping CO2 spins the arm in a circle.

1N30 - Collisions in One Dimension

Newton’s Cradle (1N30.10) 5 stainless steel balls demonstrate conservation of momentum and energy.

Eleven Pool Balls (1N30.15) Eleven pool balls are suspended linearly. One or more balls can be separated together and released to collide with the remaining balls, and the same number of balls fly off other end. This is similar to the Newton’s Cradle above, but doesn’t work quite as well because the pool balls have a lower coefficient of restitution than the stainless steel balls.

Collision Balls (Various Masses) (1N30.20) Two balls are suspended side by side so that one may be swung out and released to strike the other. Available in mass ratios of 1:1, 1:3, and 1:80. Velcro may be used on the 1:1 balls to produce inelastic collisions.

Double Ball Drop (1N30.60) A tennis ball and basketball are dropped with one on top of the other.

Astro-Blaster Toy Five rubber balls of diminishing size are threaded on a common rod through holes in their middles. The balls are free to slide on the rod, but only the top (smallest) ball is free to come off the rod. If the stack of balls is dropped on the floor, the ratio of the ball masses is such that most of the momentum and energy of the four lower balls is transferred into the top ball during the collision with the floor. The top ball flies off the stick to a much greater height than the drop height.

1N40 - Collisions in Two Dimensions

1Q10 - Moment of Inertia

1Q20 - Rotational Energy

Angular Acceleration Machine (1Q20.10) A flat bar free to rotate about its center is accelerated by the torque provided by a string-wrapped disc and hanging weight. Two weights attached to the bar may be removed, placed close to the center of the bar or at the ends of the bar for three different moments of inertia. Accelerating weights may be varied, and can be hung on either a 5 cm or 10 cm disc to change torque - observe varying angular accelerations.

Spool Wheel on Incline (1Q20.30) A large spool with a small hub rolls down an incline on the hub. When it nears the bottom of the incline the large outer discs touch down and the wheel rolls on the discs instead of the hub. Since points on the edge of the outer discs have a much greater translational velocity than points on the hub, the wheel as a whole gains translational velocity. To compensate, it loses rotational velocity.

Bicycle Wheel on Incline with Lockable Hub (1Q20.35) A bicycle wheel with a center hub that can be left free to rotate or locked to the wheel rolls down an incline on the hub. When the hub is locked, a large amount of energy must go into the angular momentum of the wheel as it rolls, so the translational velocity is much lower than with the hub free.

Falling Chimney (Faster Than g) (1Q20.50) Two boards are fixed together by a hinge at one end so as to allow them to fold together. One board is flat on the table and the other board is propped up by a stick, with a ball balanced on a golf tee attached to the end of the board. When the stick is pulled away and the board is released to free fall, there is a torque about the hinge and rotates as it falls. The rotation causes the end below the ball to accelerate faster than the ball and the ball falls into the cup.

1Q30 - Transfer of Angular Momentum

Satellite Derotator (1Q30.25) Two heavy weights on cables are released from a vertically spinning disc to stop the system by conservation of angular momentum.

1Q40 - Conservation of Angular Momentum

Rotating Stool and Weights (1Q40.10) Sit on a rotating stool holding a dumbell in each hand; pulling the dumbells inward will increase your angular velocity, letting them out will decrease it.

Watt's Governor (1Q40.23) A small model of a Watt governor is spun to increase angular velocity.

Rotating Stool and Bicycle Wheel (1Q40.30) Sit on a rotating stool holding a spinning bicycle wheel in your hands. Tip the wheel and the stool will rotate to conserve the angular momentum of the system.

Wheel and Brake (1Q40.45) A horizontal bicycle wheel is contained in a frame that is free to rotate in the same plane as the wheel. A braking device mounted to the frame is held open by a string; burn the string and the brake clamps down on the wheel, transferring angular momentum from the wheel to the frame and making both rotate together at a lower velocity.

Marbles and Funnel (1Q40.70) Marbles roll into a large glass funnel. The marbles spiral downward and rapidly increase their rate of rotation, due to conservation of angular momentum. Finally they reach an equilibrium level where they revolve in a nearly horizontal plane, gradually dropping lower as friction slows them down.

Air Rotator with Deflectors (1Q40.82) A rotating bar has tangential air jets at the ends of the arms and deflectors which may be swung into the air streams. If the deflectors are out of the air streams, the device will rotate like a garden sprinkler. If the deflectors are in, and air velocity is low, no rotation is observed because the reaction force of the air leaving the jet is balanced by the force of the air striking the deflectors.

1Q50 - Gyroscopes

Gyroscopes Choose from various gyroscopes, from simple toys to high quality demonstration models. Select this entry for general gyroscope info and references.

Handheld Gyroscope A gimbal mounted gyroscope will maintain its axis of rotation when it is moved around the room.

Gyroscope with Adjustable Weight (1Q50.20) A small gyroscope with a movable counterweight on its axis for precession.

Bicycle Wheel on Gimbals (1Q50.22) A heavy bicycle wheel in two-axis gimbals.

Bicycle Wheel Precession (1Q50.23) A bicycle wheel with handles which may be spun up with a string wrapped around the hub. It can then be suspended by a rope tied to one handle to show precession. Will also precess when stood on its end like a top.

Double Bicycle Wheel (1Q50.25) Two bicycle wheels on a common axis. If they are rotating in the same direction they will precess, but if they are rotating in opposite directions their net angular momentum is zero and they simply fall over.

Motorized Gyroscope (Precession and Nutation) (1Q50.30) A motorized gyroscope with a heavy flywheel on gimbals. Weights may be hung from the end of the bearing arm to produce precession and nutation. The flywheel takes over a minute to come up to full speed, and if a weight is hung on the arm when the spin is still slow, precession will initially be rapid but will slow down as the flywheel speeds up.

1Q60 - Rotational Stability

Tippy Top (1Q60.30) A top that flips upside down and spins on its handle.

1R10 - Hooke's Law

1R20 - Tensile and Compressive Stress

High and Low Elastic Limits (1R20.11) A plastic slinky spring may be stretched a long way and will still return to its original length. A copper coil stretched even a short distance won't return to its original length.

Young's Modulus (1R20.15) A long wire mounted in a vertical stand has a weight hanger on one end and a small platform partway down on which a pivoting mirror sits. Add weights to the weight hanger and the wire stretches, pivoting the mirror and deflecting a laser beam. The spot on the wall moves farther with each added weight.

1R30 - Shear Stress

1R40 - Coefficient of Restitution

Happy and Sad Balls (1R40.30) Two rubber balls that look similar but have different elasticities are dropped on a table. One bounces, one doesn't.

1R50 - Crystal Structure

2A10 - Force of Surface Tension

Floating Metals (2A10.20) A sewing needle, paperclip, or a piece of Aluminum foil floating on water.

Surface Tension Disc (2A10.33) Lift a floating disc off a water surface with a spring or spring scale to show the force needed to overcome surface tension.

Pepper and Soap (2A10.40) Black pepper is sprinkled on a dish of water. Add a drop of soap in the middle.

2A15 - Minimal Surface

2A20 - Capillary Action

Capillary Tubes (2A20.10) Glass capillary tubes with different size bores all sit in a reservoir of colored water - the water rises to different heights in each tube.

2B20 - Static Pressure

Pascal's Vases (2B20.42) Tubes of various shapes rise from a common horizontal tube. When filled with water, the level is the same in each tube.

Hydraulic Press (2B20.60) A hydraulic press with a large pressure gauge easily breaks boards.

2B30 - Atmospheric Pressure

Magdeburg Hemispheres (2B30.30) Two small hemispheres with handles are pressed together and evacuated; they cannot be separated by hand due to the unbalanced pressure on the outside.

Suction Cup (2B30.36) A large, 4" diameter, suction cup of the type used to carry large panes of glass has a small hole in the top. If the suction cup is squeezed down onto a table and the hole covered with a finger, a student will not be able to pull the suction cup off the table as long as your finger covers the hole.

Stool and Rubber Sheet (2B30.50) A square rubber sheet with an attached handle is set on top of a wooden stool or other heavy object. The weight of the sheet drives the air out from beneath it, and the air pressure on the outside holds the sheet and stool together. The stool can now be lifted by pulling up on the handle.

Vacuum Cannon (2B30.70) A long PVC pipe contains a ping pong ball at one end. Both ends are sealed and the tube is then evacuated by a vacuum pump. When the seal is broken at the end with the ping pong ball, atmospheric pressure accelerates the ball and gives it enough kinetic energy to destroy empty aluminum cans.

2B35 - Measuring Pressure

2B40 - Density and Buoyancy

Buoyant Force (2B40.14) Two large scales show the weights of a container of water and of an aluminum cylinder. When the cylinder is lowered into the water, its weight as shown on the scale decreases; the weight reading of the water container simultaneously increases by the same amount.

Archimedes' Principle and Crown (2B40.20) A spring scale supports a plastic bottle and an aluminum cylinder on a string. The aluminum cylinder is lowered into a water bath and the displaced water that spills out is collected in a large beaker. The weight reduction of the cylinder is noted on the scale. Then the water that was displaced is poured into the plastic bottle tied to the scale and the scale reading returns to its original value, showing that the buoyant force is equal to the weight of water displaced. Can be repeated with an irregularly shaped object (a gold crown) to find that it is, unfortunately, a fake.

Float a Battleship in a Bathtub (2B40.25) A large block of wood will float in a container that is only slightly larger with a small amount of water.

Cartesian Diver (2B40.30) A Cartesian diver is controlled by squeezing a bulb attached to the water column. Increased pressure decreases the air volume in the diver and lowers its buoyancy so it sinks. Release the pressure and the diver returns to the top.

Weight of Air (2B40.45) An evacuated 1 liter flask is placed on a digital scale. Air is then readmitted to the flask, and the extra weight of the air increases the reading on the scale.

Water and Mercury in U-Tube (2B40.53) Measure heights of liquid boundaries and use the data to calculate relative densities.

Hydrometer (2B40.60) Hydrometers float in two different liquids to demonstrate liquid density measurement and buoyancy.

Different Density Woods (2B40.61) Three similarly sized blocks of wood float at different depths, or simply sink in water. Unfortunately the type of wood is unknown.

Density Balls in Beans (2B40.85) A ping pong ball will rise and a steel ball will sink in a shaken beaker of beans.

2B60 - Siphons, Fountains, Pumps

2C10 - Flow Rate

2C20 - Forces in Moving Fluids

Pitot Tube (2C20.25) A pitot tube is connected to a water manometer and the air stream velocity is varied.

Ball in an Air Jet (2C20.30) A high velocity air stream supports large styrofoam balls and holds them in place due to the greater pressure outside the air jet.

Ball in a Funnel (2C20.35) Air blowing out of an upside down funnel will hold up a ping-pong ball.

Suspended Plate in Air Jet (2C20.40) A horizontal metal plate has a hole in the center out of which air flows downward at high velocity. A second plate pushed up against the first will cling to it due to the high velocity (low pressure) of the air flowing between them.

Suspended Parallel Cards (2C20.45) Air passing between two hanging cards pulls them together.

Airplane Wing (2C20.50) A curved sheet of aluminum is lifted upwards when a high speed air jet flows over the surface.

2C30 - Viscosity

Bubbles in Oil (2C30.25) Three tubes containing different oils with different viscosities each have an air bubble at the top of the tube. Turn over the rack holding the tubes, and the bubbles will drift up at three different terminal velocities.

2C40 - Turbulent and Streamline Flow

2C50 - Vorticies

3A10 - Pendula

Simple Pendulum (3A10.10) A single simple pendulum with a length of 1 meter.

Simple Pendulums of Various Lengths and Masses (3A10.14) Simple pendulums with differing lengths (1 m or 0.25 m) and/or differing masses (wood or metal). For comparing the mass and length to the period.

Metronome as a Pendulum (3A10.21) A metronome is used as an adjustable pendulum.

Torsion Pendulum (3A10.30) A heavy disc at the end of a limber vertical rod can be set into torsional oscillation. Mass can be added to the disc to show the effect on the period of oscillation.

Variable Angle (Variable g) Pendulum (3A10.40) A physical pendulum is mounted on a bearing so the angle of the plane of oscillation can be changed.

3A15 - Physical Pendula

Physical Pendulum (3A15.20) Compare the period of a bar supported at the end with a simple pendulum that is 2/3 the length of the bar.

Hoops and Arcs (3A15.40) A full circular hoop and portions of a hoop of the same diameter pivot from a hole at the center of the periphery of each. Though they vary greatly in size, each will swing on the pivot with the same frequency of oscillation.

3A20 - Springs and Oscillators

Water in U-Tube (3A20.55) Colored water oscillates between two legs of a glass U-tube. Motion can be frozen at any point by corking one leg of the tube.

3A40 - Simple Harmonic Motion

Circular vs. Simple Harmonic Motion (Spring) (3A40.10) The shadow of a pin moving uniformly around a circle in the vertical plane is superimposed over that of an oscillating spring and weight. The shadows of the pin and the weight are synchronized so that the shadows move in unison on the screen.

3A50 - Damped Oscillators

Water Damped Spring and Weight (3A50.10) A weight on the end of a hand held spring is set oscillating in a water column and quickly damps out.

3A60 - Driven Mechanical Resonance

Resonant Driven Pendula (3A60.31) Three simple pendula of different lengths are hung from a horizontal bar with an attached driver pendulum. The driver pendulum is a stiff rod with an adjustable bob so that its frequency can be changed. The driver pendulum is set to the natural frequency of each pendulum in turn, and only that one pendulum oscillates.

Driven Spring and Weight (3A60.43) A mass on a spring is driven at an adjustable frequency. Damping the motion in a cylinder of water shows a small shift in the resonant frequency of the oscillator.

Driven Spring and Weight with Display (3A60.43) A newer version of the above demo (Driven Spring and Weight) but also has a marker for increased visibility.

Reed Tachometer (3A60.50) A set of metal reeds of descending natural frequencies is attached to a gyroscope. The gyroscope is slightly off balance so that it vibrates as it spins, and as its rotational frequency passes through the frequencies of the reeds each reed vibrates in turn.

3A70 - Coupled Oscillations

Spontaneous Synchronization in Metronomes (3A70.23) Five small metronomes on a lightweight board are set to the same frequency and started oscillating out of phase. At first the board sits on the table and the metronomes will oscillate independently. The board is then placed on two empty aluminum cans (on their sides) to provide some light coupling between the metronomes. The metronomes will phase lock with each other within a minute or two and their 'tick-tocks' will all be in unison.

Coupled Pendula (3A70.25) Two identical massive bobs at the ends of two pendulum rods are coupled by a spring and set swinging. Alternately each one stops oscillating as its energy is transferred to the other, then begins swinging again as the energy is transferred back. Different springs change the amount of coupling and the time required for total energy transfer.

3A75 - Normal Modes

3A80 - Lissajous Figures

3A95 - Non-Linear Systems

3B10 - Transverse Pulses and Waves

Transverse Waves (Bell Labs Wave Machine) (3B10.30) Rods are arranged like ribs along a square wire "spine." A torsional wave can be sent down the spine by sharply displacing the tip of the first rod. As the wave propagates along the spine, each rod is tipped in turn by the passage of the wave, and the displacement of the ends of the rods is visible to the class, appearing as a transverse wave (visibility can be increased by illuminating the fluorescent tips of the rods with UV).

3B20 - Longitudinal Pulses and Waves

Longitudinal Waves (Hanging Slinky) (3B20.10) Longitudinal waves propagate slowly on a large plastic slinky suspended horizontally. The slinky is hand driven and can be used to show single pulses or standing waves. Paper markers hang on the coils to increase visibility of compression and rarefaction. The far end can be free or fixed. Note: This is on the same setup as Transverse Waves (Bell Labs Wave Machine) (3B10.30).

Pasco Longitudinal Wave Model (3B20.30) The Pasco Longitudinal Wave Model is a series of vertical rods, the pivot at their centers, and are connected by springs.

3B22 - Standing Waves

Standing Transverse Waves (Driven Waves in Rubber Tubing) (3B22.10) A long piece of rubber tubing is stretched out horizontally and run over a pulley at one end, then tensioned with a hanging weight. At the other end a revolving bar strikes the tubing at a frequency which can be adjusted with a motor speed controller. Transverse waves of various frequency can thus be sent along the tubing, and when the right frequencies are reached the tubing vibrates in various standing wave modes. 1 kg and 0.25 kg masses can be used to vary the tension.

3B25 - Impedance and Dispersion

Bell Labs Machine - Impedance Matching (3B25.10) The long and short rod sections of the wave machine can either be connected abruptly (unmatched coupling) or with a section of gradually lengthening rods (matched coupling).

Bell Labs Wave Machine - Reflection (3B25.20) The Bell Labs Wave Machine with the end fixed, damped, or free to show the affect on the reflected wave.

Acoustic Coupling with a Speaker (3B25.35) A small speaker has a coupling horn which may be removed. With the horn on, the sound is much louder than with the horn off.

3B27 - Compound Waves

3B30 - Wave Properties of Sound

Phonodeik Status: Unavailable Shows the deflection of a light beam which is reflected from a delicate mirror on the diaphragm of a mechanical microphone during oscillation. An "oscilloscope" from the pre-electronic era of candle flames, levers, and ingenuity. Note: For show and tell only right now.

Light and Siren in Vacuum (3B30.3) A buzzer and a LED are mounted inside a bell jar. The air is then evacuated from the jar, and although the LED can still be seen, no sound can be heard from the siren. Also listed as 6A02.10.

3B40 - Doppler Effect

Doppler Effect (3B40.10) The pitch from a siren rises and falls as it is swung around overhead.

Doppler Reed (3B40.25) A reed mounted on the end of a rotating arm produces a tone whose pitch wobbles up and down as the arm rotates.

3B50 - Interference and Diffraction

Moire Pattern (3B50.40) Two identical patterns of concentric circles are superimposed on an overhead projector or under the document camera. The separation between their centers changes by sliding one across the other and prodcues interference patterns.

3B55 - Interference and Diffraction of Sound

Two Speaker Interference (3B55.10) Two speakers driven from a common source are mounted at the ends of a long horizontal bar. The bar can be rotated to sweep the nodes and antinodes through the class.

3B60 - Beats

Beats from Tuning Forks (3B60.11) Two matched tuning forks are used, one of which has an adjustable weight on one tine. By adjusting the weight, the forks can be set to either equal frequencies or slightly different frequencies to produce beats.

Beats from Organ Pipes (3B60.13) Two large metal pipes mounted vertically on the lecture table will resonate at low frequencies when a source of "white noise" (a Fisher burner) is placed at the bottom end. If both pipes are excited they will produce beats.

Beats from Singing Glass Tubes (3B60.16) Two small glass Rijke tubes (3D30.70) have electrically heated wire grids and moveable tubes. Move a tube so that the grid is at the 1/4 point and the tube will "sing." Put it anywhere else, and it won’t. Since the tubes are slightly different lengths, running them both together produces beats.

Beats from Two Speakers Two speakers with separate audio oscillators produce beats.

3B70 - Coupled Resonators

3C10 - The Ear

3C20 - Pitch

Siren Disc (3C20.30) A disc with eight rings of uniformly spaced holes and a ninth ring of randomly spaced holes. The disc is spun by a motor and an air jet is directed at the holes. Puffs of air through the disc as a hole passes the air jet produce pressure variations, and thus sound. Different musical notes are heard from different rings of regularly spaced holes but noise is heard from the ring of randomly spaced holes.

3C30 - Intensity and Attenuation

Decibel Meter (3C30.22) A sound level meter with output measured in decibels. Try it with your voice, a buzzer, or various instruments. Used under the document camera.

3C50 - Wave Analysis and Synthesis

Pasco Fourier Synthesizer (3C50.10) The Pasco Fourier Synthesizer is connected to a speaker and an oscilloscope. The synthesizer can generate two fundamentals of 440 Hz and eight higher harmonics, each with amplitude and phase control. The synthesizer can produce either sine, square or triangular wave forms. Note: While it works fine, there are several nice java applets available.

3C55 - Music Perception and the Voice

3D20 - Resonance in Strings

Sonometer (3D20.10) The ends of a stretched steel wire are hooked to an audio amplifier and a small horseshoe magnet is placed over the wire, so that transverse vibrations of the wire are transformed into currents along the wire. The currents are amplified and fed into an oscilloscope to display the waveform. The wire is finger plucked, and both tension and length are adjustable. Harmonics can be either ignored or intensified by changing placement of the magnet, and can also be damped out selectively with a small brush.

3D22 - Stringed Instruments

3D30 - Resonance Cavities

Vertical Resonance Tube (256/512 Hz) (3D30.10) A glass cylinder is filled with water to one of two preset levels and the tuning fork with a frequency equal to the resonant frequency for that level is held over the opening. It is noted that the sound is much louder than when the tube is filled to any other level.

Open and Closed Resonance Tube (256/512 Hz) (3D30.20) A metal tube is cut to length to resonate at 256 Hz when closed and 512 Hz when open.

Helmholtz Resonators (3D30.40) Spherical cavities can be made to resonate loudly by a tuning fork of the corresponding frequency.

3D32 - Air Column Instruments

Open and Closed End Pipes (3D32.25) A variety of organ pipes with different lengths and removeable end pieces to show the effects of pipe length and the difference between open and closed end resonators.

3D40 - Resonance in Plates, Bars, Solids

Xylophones Wood or metal xylophones covering an octave or two.

Rectangular Bar Oscillations (3D40.11) A long metal bar with a rectangular cross section. A high pitch longitudinal oscillation is excited by hammering the end. Two lower transverse frequencies are excited by striking one side or the other of the bar, with the wider side having the lower frequency.

Water Spouting Bowl (3D40.51) A 15" diameter decorative bowl with handles is partially filled with water. Wet your hands and then rub the handles to create resonance. The standing wave will cause the water to jump up several inches or more.

3D46 - Tuning Forks

Tuning Forks (3D46.15) Various tuning forks for show and tell.

3E20 - Loudspeakers

4A10 - Thermometry

Show & Tell Thermometers (4A10.10) Various thermometer types including liquid (alcohol or mercury), bimetallic coil, liquid crystal, thermocouples, or IR.

4A20 - Liquid Expansion

Thermal Expansion of Water (4A20.10) A flask filled with colored water has a long glass tube protruding up from the neck. A gas flame is placed under the flask and thermal expansion forces water up the tube.

4A30 - Solid Expansion

Bimetallic Strip (4A30.10) Two different metal strips bonded together and fastened to a handle. When heated, the strip bends because of the different expansion rates of the metals.

Bimetallic Coil Same as the bimetallic strip, but helical in form. The coil is heated and moves a large indicator arrow as it expands.

Ball and Ring (4A30.21) A metal ball and ring on handles are constructed so that the ball will just pass through the ring at room temperature. The ball is heated and will not pass through the ring. The ball and ring are both heated and the ball now passes through the heated ring.

Ball and Hole (4A30.22) A ball which is too large to pass through a hole in a square metal plate will pass easily through the hole after the plate has been heated in a flame. Many students expect the hole to shrink upon heating, but it actually expands along with the rest of the plate.

4A40 - Properties of Materials at Low Temperatures

4B10 - Heat Capacity and Specific Heat

Ruchardt's Experiment for gamma (Cp/Cv) (4B10.70) A steel ball in a precision tube oscillates as gas escapes from a slightly overpressured flask. By measuring the oscillation frequency, you can determine the ratio gamma = Cp/Cv. Note: Please talk to us in advance.

4B20 - Convection

Convection in Square Tube (4B20.10) A large glass square loop is filled with water and heated by a burner near one bottom corner. The resulting circulating convection current is shown by adding drops of dye to the water.

Convection Currents Projection (4B20.40) Convection currents from a hot filament in a small water cell are projected onto a screen using a simple Schlieren optics system.

4B30 - Conduction

Thermal Conductivity (4B30.12) Five rods of different composition are attached to a steam chamber to provide equal temperatures at the bases of the rods. The rods are covered with wax, which melts and peels off as the rods heat up. Relative rates of heat conduction can be deduced from the rates at which the wax melts on each rod. The five materials in order of decreasing conductivity are: copper, aluminum, brass, steel, and glass.

4B40 - Radiation

Radiation from Hot and Cold Bodies Two parabolic reflectors are aligned facing each other, with a thermopile at the focal point of one of the reflectors and a heated sphere at the other. A projection galvanometer's deflection shows the transmission of heat by radiation. Replace the hot sphere with a sphere dipped in liquid nitrogen and the galvanometer will deflect in the opposite direction (showing that the thermopile itself is radiating and heat flows to the cold sphere).

4B50 - Heat Transfer Applications

Insulation (Dewar Flasks) (4B50.10) Four dewar flasks (thermos bottles) are filled with boiling water and a thermocouple is placed in each. Each flask has a different degree of insulation, and these are (from worst to best): unsilvered without vacuum between the walls, silvered without vacuum, unsilvered with vacuum, and silvered with vacuum. The water temperature is measured throughout the class period and compared to an uninsulated beaker. Temperatures are collected and displayed via a LabVIEW program and a laptop plugged into the projector.

4B60 - Mechanical Equivalent of Heat

Drill and Dowel (4B60.55) A wooden dowel held in an electric drill chuck is ground against a large flat piece of wood. The friction between the two produces heat and smoke.

Cork Popper (4B60.70) A motorized rotating hollow shaft holds a thimblefull of water and is sealed with a stopper. Wood brakes are squeezed together on either side of the rotating shaft, and the heat generated by friction boils the water and pops the cork.

4B70 - Adiabatic Processes

4C10 - PVT Surfaces

PVT Surface Model - Ideal Gas (4C10.10) A three dimensional model showing various PVT states of an ideal gas.

PVT Surface Model - Carbon Dioxide (4C10.10) A three dimensional model showing various PVT states of carbon dioxide.

PVT Surface Model - Water (4C10.10) A three dimensional model showing various PVT states of water.

4C20 - Phase Changes: Liquid - Solid

Thermite An extremely exothermic reaction between Iron Oxide (rust) and Aluminum produces liquid Iron.

4C30 - Phase Changes: Liquid - Gas

4C31 - Cooling by Evaporation

Drinking Bird (4C31.30) Commercial novelty item. Dip the bird's beak into a beaker of water, then let it go. Evaporation of the water from the wet beak cools the beak, lowering the vapor pressure of the liquid inside and drawing it up into the head. That overbalances the bird and it tips into the water for a "drink." In that position, the liquid inside flows back into the lower bulb, which rights the bird and starts the cycle over. Note: This is not very visable for a large class without using a camera.

4C33 - Vapor Pressure

Hand Boiler (Franklin's Pulse Glass) (4C33.50) A glass tube contains a small amount of a volatile liquid (Methylene Chloride). Heat from your hand will boil the liquid and the vapor pressure will force it to flow to the opposite end of the tube. Note: This is small and not very viewable for a large class.

4C40 - Sublimation

4C50 - Critical Point

Critical Point of CO2 (4C50.10) liquid CO2 in a glass tube at high pressure is close enough to the critical point that warm air from a hair dryer will complete the transition. The tube is displayed with a video camera and the meniscus is seen, but when the tube is heated the meniscus slowly fades and disappears as the liquid CO2 goes through a gradual transition to a high pressure gas. A turbulent mixture of liquid and gas with equal densities is seen above and below the miniscus point.

Critical Opalescence (4C50.20) A mixture of triethylamine and water is heated and passes through the liquid/gas critical point. The liquid is clear at first, then becomes cloudy as it approaches the critical point.

4D10 - Brownian Motion

4D20 - Mean Free Path

Crooke’s Radiometer (4D20.10) A partially evacuated glass bulb holds a pinwheel where the vanes are reflective on one side and painted black on the other. Light from an incandescent lamp will be absorbed by the dark side of the vanes, heating the nearby air, and causing the pinwheel to rotate towards the reflective side of the vanes.

4D30 - Kinetic Motion

4D50 - Diffusion and Osmosis

Bromine Diffusion (4D50.45) Two glass tubes containing bromine and bromine/air are cooled in liquid nitrogen and allowed to warm back up to show rates of diffusion. The bromine only tube will diffuse faster than the bromine/air mixture.

4E10 - Constant Pressure

Galileo's Thermometer (Thermal Expansion of Air) (4E10.11) Air expansion in a inverted glass bulb causes liquid level in a vertical tube below the bulb to drop.

4E20 - Constant Temperature

Boyle's Law (Pressure vs. Volume) (4E20.10) A syringe is connected to a dial pressure gauge. Compressing the syringe causes an increase in pressure.

4E30 - Constant Volume

4F10 - Entropy

Entropy Pennies A tray is filled with pennies painted green on the tails and red on the heads. If the tray is shaken the pennies begin to flip at a rate dependent on the magnitude of the shaking. Eventually an equilibrium is reached, with approximately equal numbers of reds and greens. Further shaking will not, of course, return them to their original state. If only a few pennies are used, they will occasionally return to their original state, showing the dependence upon the number of particles in the system.

Mixing and Unmixing (4F10.10) The volume between two coaxial cylinders is filled with glycerin and a thin column of red dye. When the inner cylinder is rotated, the dye appears to be mixed but is distributed in a fine cylindrical shell within the glycerin. Reversing the direction of inner cylinder rotation will cause the original dye column to reappear. Note: Please talk to us about this first.

4F30 - Heat Cycles

Heron's Engine (or Hero's Engine) (4F30.01) A working model of the first primitive steam engine. A glass globe containing a small amount of water is heated with a flame. The steam produced comes out through two arms and spins the globe.

Stirling Engines - General Information (4F30.10) Pick from the following selection. Or follow this link for general heat engine references.

Stirling Engine - Transparent Pistons Has glass cylinders so the power and displacement pistons can be viewed.

Stirling Engine - Hand Held A Stirling engine so well machined and balanced that it can run off the heat from your hand.

Stirling Engine - Heavy Duty A heavy duty Stirling engine. This is the biggest engine, but perhaps the least instructive because of low visibility.

Stirling Engine - Hot and Cold Will run in one direction when placed on a hot resevoir, and will run in reverse when placed on a cold resevoir. Note: May be out of service.

5A10 - Producing Static Charge

Basic Electrostatics Set Contains Electrostatic Rods and Cloth, Charged Rods and Pivot, and the Electroscope.

Electrostatic Rods and Cloth (5A10.10) Glass rods and silk (positive charge), clear acrylic rods and wool (positive charge), red acrylic rods and wool (negative charge), or rubber and fur (negative charge).

Electrophorus (5A10.20) An aluminum disc with an insulating handle on top of a plastic plate which has been charged by rubbing with a piece of wool. A finger or grounded wire touched to the top of the metal plate removes the induced charge that is the same polarity as the charge on the plate, then the disc is lifted off the plate, leaving the disc charged to a high voltage. This may be repeated many times without recharging the plastic.

5A20 - Coulomb's Law

Electrostatic Attraction and Repulsion (Charged Rods on Pivot) (5A20.10) Charged rods (5A10.10) on a pivoting stand are free to rotate and show attraction or repulsion between charges. Note: See also Magnetic Attraction and Repulsion (5H20.10).

Aluminized Ping Pong Balls (Electrically Connected) Two aluminum coated ping pong balls hang from wires attached to a metal plate. Touch a charged rod to the plate and the balls separate.

Aluminized Ping Pong Balls (Electrically Insulated) Two aluminum coated ping pong balls hang from a plastic rod so that they may be given opposite charges to demonstrate attraction.

5A22 - Electrostatic Meters

Electroscope (5A22.10) An electroscope to show charge. Uses a light to project the shadow onto a translucent glass screen which helps visibility at shallow viewing angles.

Electrostatic Voltmeter (5A22.50) A voltmeter which reads the potential from charged rods without affecting the charge on the rod.

5A30 - Conductors and Insulators

Conducting and Non-Conducting "T" Terminal on Electroscope (5A30.15) A large "T" shaped terminal is attached to the electroscope. One arm is made of acrylic and the other arm is aluminum, but both have a metal ball on the end. Touch a charged rod to the ball on each arm to show that only the aluminum arm conducts and charges the electroscope.

5A40 - Induced Charge

Charge by Induction (Induction Spheres) (5A40.10) Two metal spheres on insulated stands are touching each other. A charged rod is brought near one of them which induces the opposite charge on the other sphere. While the rod is held close to the first sphere, the other is moved away and touched to the electroscope.

Wood Needle (5A40.30) A wood 1x2 is placed on a rotating pivot, and will be attracted by either a positively or negatively charged rod due to induction and polarization of the water molecules within the wood.

Metal Rod on Pivot (5A40.35) An aluminum rod on a rotating stand will be attracted to a charged rod of either polarity due to induced charge in the conductor.

Kelvin Water Dropper (5A40.70) An unusual induction machine in which dripping water acts as the carrier for charge buildup in two metal cans. When a sufficiently high voltage is reached, the cans discharge through a small fluorescent bulb. Note: This is hard to see in a large class.

5A50 - Electrostatic Machines

Wimshurst Machine (5A50.10) A hand cranked generator produces sparks in the hundred kilovolt range; in principle a continuously operating electrophorus (see 5A10.20).

Van de Graaff Generator (5A50.30) A small Van de Graaff generator and a discharge wand. The generator without paper streamers will produce larger sparks than the generator with paper streamers (see 5B10.15).

5B10 - Electric Field

Van de Graaff With Streamers (5B10.15) A Van de Graaff generator with paper streamers taped to the dome shows the radial shape of the electric field produced by the generator. Can also show the distortion of the field due to the introduction of a grounded metal rod. Note: This works much more reliably than getting hair to stand up.

Bouncing Ping Pong Balls (5B10.30) A variation of Franklin's Bells. Aluminum coated ping pong balls bounce up and down between two charged metal plates due to electrostatic forces on the balls. Also shows basic charge transfer. Note: This uses the same setup at the Millikan Oil Drop Analog.

Grass Seed Electric Field (5B10.40) Electrodes of different shapes are placed in a transparent dish filled with mineral oil and a small amount of grass seed (which contains water). A Wimshurst machine is connected to the terminals and the electric field applies a force on the dipole moment of the water molecules in the grass seed. The seed will then move within the oil and bceome aligned with the electric field produced by the generator.

5B20 - Gauss' Law

Faraday Ice Pail (5B20.10) Shows that charge resides only on the outside of a hollow conductor. A metal trash can is charged using a Wimshurst machine, then the charge distribution on the can is investigated using a metal ball on an insulating rod.

Faraday Cage (5B20.30) A large mesh wire cage fits over the electroscope, shielding it from outside electric fields. A high voltage source (a charged acrylic rod) brought near the cage will not deflect the electroscope.

Radio in a Faraday Cage (5B20.35) A small AM radio is placed in a copper wire mesh cage. Note: The lecture halls themselves sometimes act as large Faraday cages and block all radio transmissions.

5B30 - Electrostatic Potential

Egg Shaped Conductor (5B30.20) A prop used to discuss charge density as a function of radius of curvature.

Van de Graaff and Discharge Wand (5B30.35) A grounded wand with a round bulb on one end and a sharp point on the other is brought near a charged Van de Graaff. The bulb end draws out impressive sparks, while the pointed end produces only corona discharge.

5C10 - Capacitors

Parallel Plate Capacitor (Variable Separation) (5C10.20) Two parallel circular metal plates which form a capacitor are supported so that the distance between them can be varied. The plates are connected to an electrostatic voltmeter and charged. As the separation varies, the changing voltage between the plates is reflected in the reading on the voltmeter. See also Parallel Plate Capacitor with Dielectrics (5C20.10).

Tuning Capacitor (Variable Area) (5C10.35) Similar to the Parallel Plate Capacitor (5C10.20), but this is a large version of the tuning capacitor used in AM radios, in which the area (overlap) between the plates can be changed.

5C20 - Dielectrics

Parallel Plate Capacitor with Dielectrics (5C20.10) Uses the Parallel Plate Capacitor (5C10.20), but instead of varying the separation, a large plastic or cardboard sheet is inserted between the plates.

Force on a Dielectric (5C20.20) Dielectrophoresis due to a non-uniform electric field at the edge of a parallel plate capacitor. A circular plastic disk on the end of a pivoting arm is balanced between and slightly above the plates of a large parallel plate capacitor. As the capacitor is charged, the force on the dielectric pulls it down between the plates.

Dissectable Leyden Jar (5C20.30) A Leyden jar with removeable inner and outer conductors is charged with a Wimshurst machine then discharged with a large spark. The Leyden jar is charged again, then disassembled by removing the inner and outer conductors. These can be touched together, grounded, etc., and no sparks are seen. However, if the Leyden jar is now reassembled and discharged, the spark will be almost as large as the original spark. Note: Please see us beforehand about technique.

5C30 - Energy Stored in a Capacitor

Exploding Capacitor (Show & Tell Only) (5C30.20) Status: Unavailable Three 1500 mF capacitors connected in parallel and rated for 400 volts. A shorting bar shows the stored energy could melt and vaporize metals. This configuration is no longer used or charged due to safety concerns.

Series and Parallel Capacitors (5C30.42) Two capacitors mounted on a board which can be used individually, in series, or in parallel. After a combination has been charged to 1.5 V, it is discharged through a projection ballistic galvanometer, and the amount of charge the combination held is reflected in the displacement in the galvanometer. Note: Capacitance of each can vary by +/- 20% so the parallel capactitance is the sum of the two and not necessarily twice either individual capacitance.

5D10 - Resistance Characteristics

Resistance Wires (5D10.20) One board containing five wires of different lengths, areas, and materials. Each of the wires is hooked in turn across a battery and the current through the wire is shown on a large meter. The dependence of resistance on length, area, and composition of the wire can be shown. See also Ohm's Law (5F10.10) and Series and Parallel Resistance (5F20.55).

5D20 - Resistivity and Temperature

5D30 - Conduction in Solutions

5D40 - Conduction in Gases

Jacob's Ladder (5D40.10) A classic electrical display often seen in the background of mad scientist B movies. Two long vertical electrodes are close together at the bottom, but separate gradually towards the top. 15,000 Volts from a transformer starts an arc at the bottom. Since the voltage is AC the arc breaks as the voltage decreases; the ionized air that was heated during the arc rises while the arc is off. When the AC voltage again becomes high enough to strike an arc, it goes through the ionized air that has risen above the point of the previous arc. The process continues until the arc reaches the top of the electrodes, where it breaks off and reforms at the bottom to begin the cycle again.

Neon Lamp (5D40.50) A neon lamp does not conduct below 80 V, but passes current easily above that voltage, and will continue to carry current down to about 60 volts once the current has been started.

5E20 - Electrolysis

Electrolysis of Water (5E20.10) DC through slightly acidic water produces hydrogen and oxygen at the electrodes. Matches are provided to ignite the Hydrogen.

5E30 - Plating

5E40 - Cells and Batteries

5E50 - Thermoelectricity

5E60 - Piezoelectricity

5F10 - Ohm's Law

Ohm's Law (5F10.10) Uses the Resistance Wires (5D10.20) board described above, but in this demo the voltage is also varied.

5F15 - Power and Energy

I^2R Losses (5F15.45) Nichrome, iron, and copper wires are wired in series with a Variac. A small paper rider is wrapped around each wire. As the voltage is increased, the wires begin to heat up in order of decreasing resistance. Although the current is the same for all wires, the wire with the biggest resistance (nichrome) heats up first and burns its paper rider. Increasing the voltage (and thus the current) further makes the iron wire burn its paper rider and makes the nichrome glow red-hot. The copper wire barely gets warm.

5F20 - Circuit Analysis

Wheatstone Bridge (5F20.40) Measure resistance by balancing voltage drops over two different paths, one of which includes the resistor to be measured. Three types are available: (1) With Lamps to show the principle but not make actual measurements, (2) With a sliding wire to make actual measurements, and (3) A commercial bridge as a show-and-tell item.

Series and Parallel Resistance (5F20.55) Two identical resistance wires on a board are connected to a battery, either individually, in series, or in parallel. The current for the different configurations is measured with a large meter.

5F30 - RC Circuits

Relaxation Oscillator (5F30.60) A capacitor, resistor, and DC power supply are wired in series, with a neon bulb in parallel with the capacitor. The capacitor charges to about 80 V (the breakdown voltage of the neon bulb), then discharges through the bulb and begins the cycle again. The capacitor voltage can be plotted on an oscilloscope.

Emergency Flasher A commercial emergency flasher uses a 9V battery to flash a neon lamp at approximately 2 Hz. The battery voltage is stepped up internally to provide the 600 Volts needed to flash the tube.

5F40 - Instruments

5G10 - Magnets

5G20 - Magnetic Domains and Magnetization

5G30 - Paramagnetism and Diamagnetism

5G40 - Hysteresis

5G50 - Temperature and Magnetism

5H10 - Magnetic Fields

5H15 - Fields and Currents

5H20 - Forces on Magnets

5H25 - Magnet/Electromagnet Interactions

5H30 - Force on Moving Charges

5H40 - Force on Current in Wires

5H50 - Torques on Coils

5J10 - Self Inductance

5J20 - LR Circuits

5J30 - RLC Circuits - DC

5K10 - Induced Currents and Forces

5K20 - Eddy Currents

5K30 - Transformers

5K40 - Motors and Generators

5L20 - RLC Circuits - AC

5L30 - Filters and Rectifiers

5M10 - Semiconductors

5N10 - Transmission Lines and Antennas

5N20 - Tesla Coil

Ruhmkorff Induction Coil (5N20.10) An induction coil with mechanical "make and break" oscillator produces approximately 100 kV sparks.

5N30 - Electromagnetic Spectrum

6A2 - Straight Line Propagation

6A10 - Reflection from Flat Surfaces

6A20 - Reflection from Curved Surfaces

6A40 - Refractive Index

6A42 - Refraction from Flat Surfaces

6A44 - Total Internal Reflection

6A46 - Rainbow

6A60 - Thin Lens

6A61 - Pinhole

6A65 - Thick Lens

6A70 - Optical Instruments

6B10 - Luminosity

6B40 - Blackbodies

Bichsel Boxes (6B40.20) Two 3x5 index card boxes each with a small hole in the lid; one is painted black inside and the other white. Hold the boxes up to the students with the holes facing them and they appear almost identical. Open the lids and the difference is obvious. Useful in discussing blackbody cavity radiation.

6C10 - Diffraction Through One Slit

6C20 - Diffraction Around Objects

6D10 - Interference From Two Sources

6D20 - Gratings

6D30 - Thin Films

6D40 - Interferometers

6F10 - Synthesis and Analysis of Color

6F40 - Scattering

6H10 - Dichroic Polarization

6H20 - Polarization by Reflection

6H30 - Circular Polarization

6H35 - Birefringence

6H50 - Polarization by Scattering

6J10 - The Eye

6J11 - Physiology

6Q10 - Holography

7A10 - Photoelectric Effect

7A15 - Millikan Oil Drop

7A50 - Wave Mechanics

7A55 - Particle/Wave Duality

7A60 - X-ray and Electron Diffraction

7A70 - Condensed Matter

7B10 - Spectra

7B11 - Absorption

7B13 - Resonance Radiation

7B30 - Ionization Potential

7B35 - Electron Properties

7D10 - Radioactivity

7D30 - Particle Detectors

7D50 - Models of the Nucleus

7F10 - Special Relativity