Answer:
folk dancing is old music and ball room is young dancing
A transverse wave (electromagnetic wave) carries energy through space.
Mechanical energy is the answer
The green is ground. Ideally, no current travels in this one. The red and black are the power and neutral wires but which colors they are depends on a convention. In the US, you will actually have a black (power) and a white (neutral) Here it's red and black and usually in a red/black system the red is the power. Either way there is a potential of 120V rms between them.
