An AC adapter for a telephone answering machine uses a transformer to reduce the

Question

An AC adapter for a telephone answering machine uses a transformer to reduce the line voltage of 120 V to a voltage of 7.00 V. The RMS currentdelivered to the answering machine is 449 mA. If the primary (input) coil of the transformer has 480 turns, then how many turns are there on the secondary (output) coil?

What is the power drawn from the electric outlet, if the transformer is assumed to be ideal?

What is the power drawn by the transformer, if 15.8 percent of the input power is dissipated as heat by the eddy currents in the iron core?

Explanation / Answer

a) Assuming there are no copper losses (Ideal transformer) V1/V2 = N1/N2 120/9 = 240/N2 So Secondary coil has 18 turns. b) Power delivered to the transformer = Power output from the transformer (Assuming Ideal transformer) = 9*0.44 = 3.96 VA

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