Author Question: Transmitting power at high voltage, e.g., 400,000 V, reduces the power loss for transmission lines. ... (Read 80 times)

JGIBBSON · **on:** Jul 28, 2018

Transmitting power at high voltage, e.g., 400,000 V, reduces the power loss for transmission lines. But such a voltage would destroy electrical devices in household use. How then can such 400,000 V electricity be used in a normal house?
a. The ground prongs on household plugs reduce the voltage to 120 V.
b. Before reaching households, transformers are used to reduce the voltage appropriately.
c. No matter the incoming voltage, a 120 V device only lets 120 V in.
d. The 400,000 V is just theoretical; long distance transmission lines actually use 120 V.

Question 2

Two loudspeakers are placed facing each other and driven by the same source at 680 Hz. A listener is positioned between the two speakers on the line separating them, thus creating a constructive interference at the listener's ear. What minimum distance would one of the speakers be moved back away from the listener to produce destructive interference at the listener's ear? (The speed of sound = 340 m/s.)
a. 0.13 m
c. 0.50 m
b. 0.25 m
d. 1.00 m