A transformer is used to light 140 W , 24 V lamp from 240 V AC mains. The current in the main cable is 0 . 7 A . The efficiency of the transformer is

Question

A transformer is used to light 140 W , 24 V lamp from 240 V AC mains. The current in the main cable is 0 . 7 A . The efficiency of the transformer is, 63.8%, 84%, 83.3%, 48%

MARKS App · Accepted Answer

Mains voltage is V = 240 V and mains current is I = 0 .7 A input power will be P input = 240 × 0.7 = 168 W But output power is given as P output = 140 W Therefore efficiency = output input × 100 % = 83.33 %

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