Wed, 5 February 2014
This video consists of a few demonstrations covering the heating effect of electric currents.
1. An electric current is run through a thin metal wire. As the strength of the current increases, the wire gets warmer and warmer and it eventually starts glowing red-hot. When the current is decreased, the wire cools off.
2. The next demo shows how the resistance of a wire can be decreased by blowing air on it. An air blower is used to blow cool air on an electric heater. As the wire cools off, there is an increase in the electric current flowing through it (the settings on the power supply remains unchanged).
3. The next two demos show how a metal wire melts and breaks when the current through it is too high. This idea is used to make relatively cheap electric fuses which can protect more expensive devices from being damaged by excessively high currents.