I2R Losses (5F15.45)
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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.
1) Turn on the variac and then slowly increase the voltage to 10 to 15 Volts AC. Watch the paper loop on the Nichrome wire.
2) Keep increasing the voltage until the Iron paper starts smoking.
Do not go past 50 Volts AC!
3) Remember that the variac and multimeter show RMS values for the voltage and current.