A transformer supplies 60 watts of power to a device that is rated at 20 volts (

Question

A transformer supplies 60 watts of power to a device that is rated at 20 volts (rms). The primary coil is connected to a 120-volt (rms) ac source. What is the current I1 in the primary coil? The voltage and the current in the primary coil of a nonideal transformer are 120 volts and 2.0 amperes. The voltage and the current in the secondary coil are 19.4 volts and 11.8 amperes. What is the efficiency e of the transformer? The efficiency of a transformer is defined as the ratio of the output power to the input power, expressed as a percentage: e = 100 Pout/Pin.

Explanation / Answer

Part G :

P = power = 60 watt

Vp = primary voltage = 120

ip = primary current

P = Vp ip

ip = 60 / 120 = 0.5 A

part H

Pout = 19.4 x 11.8 = 228.92 watt

Pin = 120 x 2 = 240

e = 100 x 228.92 / 240 = 95.4

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