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 current delivered to the answering machine is 410 mA. If the primary (input) coil of the transformer has 360 turns, then how many turns are there on thé secondary (output) coil? 21 You are correct. Previous Tries What is the power drawn from the electric outlet, if the transformer is assumed to be ideal? 14.29 W fitnte transformer is ideal, the input and the output powers are equal to each If the transformer is ideal, the input and the output powers are equal to each other. Do we have enough information to calculate the output power? Submit Answer Incorrect. Tries 5/99 Previous Tries What is the power drawn by the transformer, if 14.5 percent of the input power is dissipated as heat in the coils and in the iron core of the transformer Submit Answer Tries 0/99

Explanation / Answer

a) Np / Ns = Vp / Vs

360 / Ns = 120 / 7

Ns = 21

b) P = V I = 7 * 410 * 10-3

= 2.87 W

c) (1 - 0.145) x = 2.87

x = 2.87 / (1 - 0.145)

power drawn by transformer x = 3.36 W

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