DENJIRO: I have here an average 100 V outlet. If you look closely, the size of the two slots are different. There’s actually a little secret hidden here. Let me plug an electroscope into the shorter slot. An electric current passes through, and the light bulb turns on. Now, let me plug it into the longer slot.
GIRL: Huh? The light bulb doesn’t turn on.
DENJIRO: Actually, the longer slot of a 100-V outlet has 0 V. The electroscope didn’t turn on since the slot is connected to the ground wire that lets electricity escape through the ground.
NARRATOR: You may have seen a ground wire on microwaves. They let electricity escape in case of an electrical leakage. So why is there a ground wire in the outlet as well?
DENJIRO: Let me explain using this model. These two coils represent the transformer of a utility pole. It reduces the 6,600-V current from the power plant to 200 V and sends the electricity to your home through red, white, and black wires. The red and black wires from the transformer are 100 V. One of these wires is connected to the short slot of an outlet. On the other hand, the white wire is connected to the long slot. This white wire is connected to the ground through the transformer. This is the ground wire. Since the wire is connected to the ground, even if the 6,600 V were to flow over to the side of 200 V, it would flow to the ground.
NARRATOR: A lightning rod plays the same role as a ground wire. This jar is filled with a combustible gas, but since the lightning rod is properly grounded… nothing happens even if lightning strikes the rod.
DENJIRO: However, let me disconnect the two metal rods so that the lightning rod is not grounded. See what happens when lightning strikes now. There was a discharge at the space between the two metal rods, and the gas caught fire.
NARRATOR: A ground wire ensures that we can safely use electricity.
DENJIRO: I hope energy will bring you all happiness. Our magic word is "Happy Energy!”