[quote]原帖由
Light2012 於 2014-12-17 11:08 PM 發表
1. The rating of an air-conditioner is '200V, 60Hz, 2500W'. Explain what is meant by (a) 200V; (b) 60Hz; and (c) 2500W.
Sol: Rating: If the air-conditioner is connected to a 200 V r.m.s. supply, the power supplied to the air-conditioner is 2500W.
Frequency = 60 Hz means in 1 second, the current changes direction 100 times.
2. Explain how the following designs ensure our safety.
(a) In a plug, the earth pin is longer than the live pin and the neutral pin.
Sol: It ensure that the Earth pin is connected to the ground before the live and neutral pin. Therefore, in case there is current leakage, the current will flow through the Earth wire instead of human body touching the metal case.
(b) A fuse is connected to the live wire instead of the neutral wire.
Sol: It ensure that when the fuse blown, the electrical appliance is
disconnected from "High Potential"!!! The change of getting electric shock is lower!
Remember, it is nothing to do with the complete circuit or not!