A step-down transformer is used to convert 220 V AC to 11 V AC. The primary coil has 2000 turns. If the efficiency of the transformer is 90% , and the output power is 99 W , what is the current in the

Question

A step-down transformer is used to convert 220 V AC to 11 V AC. The primary coil has 2000 turns. If the efficiency of the transformer is 90% , and the output power is 99 W , what is the current in the primary coil?

TestHub · Accepted Answer

Given: V p ​ = 220 V , V s ​ = 11 V . Efficiency η = 90% = 0.9 . Output power P s ​ = 99 W . Efficiency is defined as η = P p ​ P s ​ ​ , where P p ​ is the input power. So, P p ​ = η P s ​ ​ = 0.9 99 W ​ = 110 W . The input power is also P p ​ = V p ​ I p ​ . Therefore, I p ​ = V p ​ P p ​ ​ = 220 V 110 W ​ = 0.5 A .

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