DENJIRO: Today, I’d like to show you an experiment involving a device for safely using electricity. Take a look at this. There is a thin piece of aluminum foil. A metal like aluminum conducts electricity well. Now, what will happen if we run a large amount of electricity through the aluminum at once? Three, two, one, go!
The aluminum foil melted.
NARRATOR: A device that uses the same principle of how electricity can melt metal and is often found inside electrical appliances is the fuse. A fuse prevents electrical appliances from breaking when a current that exceeds a certain level flows through it.
DENJIRO: I’m going to attach light bulbs to a fuse one by one. As I add more light bulbs, the wire in the fuse glows red. It eventually melts. When more current than necessary flows through, the fuse gets blown, and it prevents an excessive current from breaking an electrical appliance.
A device that plays the same role as a fuse is attached to the distribution board inside a home. That is the circuit breaker. I have here an actual circuit breaker. It is connected to an electric stove and two hot plates. Now, I’m going to put the stove on high heat to have lots of electricity flow to it.
BOY: It turned off!
DENJIRO: The circuit breaker tripped. Let’s see how this works. Inside the circuit breaker is a bi-metal, which has two pieces of metal stuck together. When the bi-metal is heated by a large current, it bends due to a difference in the coefficient of thermal expansion of the two metals. When the bi-metal bends by a certain amount, the stopper is released, and the switch is automatically turned off.
Electrical appliances that produce heat tend to use a lot of electricity. Both a fuse and a circuit breaker are devices that allow us to safely use electricity. Make sure not to use too much electricity!
I hope energy will bring you all happiness. Our magic word is "Happy Energy!"