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Code Number: 5D10.60
Demo Title: Burn a Resistor
Condition: Excellent
Principle: Ohms Law
Area of Study: Electricity and Magnetism
Equipment:
Resistors (22 and 2200 Ohm), Small Holder Boards, Variac with On/Off Switch, Voltmeter (if desired).
Procedure:
Connect the resistor directly to a Variac with an on/off switch. Turn on the Variac and turn up the voltage until the 22 ohm resistor bursts into flames. Turn off the Variac leaving the voltage setting where it is. Insert a 2200 ohm resistor. Turn on the Variac and observe that this resistor will handle this voltage without damage. Increase the voltage and burn this resistor if you desire noting the additional voltage increase needed.
The burnt out oven coil is an example of a terminal "increasing resistance / increasing temperature" cycle.
References:
- Borislaw Bilash II, David Maiullo, "Burn a Resistor", A Demo a Day: A Year of Physics Demonstrations, p. 268.