PLEASE EXPLAIN THE QUESTION STEP BY STEP AND EXPLAIN WHAT THE VARIABLES MEAN An

Question

PLEASE EXPLAIN THE QUESTION STEP BY STEP AND EXPLAIN WHAT THE VARIABLES MEAN

An AC adapter for a telephone answering machine uses a transformer to reduce the line voltage of 120 V to a voltage of 8.00 V. The RMS current delivered to the answering machine is 490 mA. If the primary (input) coil of the transformer has 600 turns, then how many turns are there on the secondary (output) coil?
40

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

What is the power drawn by the transformer, if 15.5 percent of the input power is dissipated as heat in the coils and in the iron core of the transformer?
4.64 W

Explanation / Answer

Apply in a transforner

Ns/Np = Vs/Vp = Is/Ip

where NS ans Np are seconda dr and primary tunrs

Vs and Vp are secondary and primary volatges

Is and Ip are secondary and prianry currents

also in ideal tansformer output P = input P

so VsIs = VpIp

so here V1 = 120 V

V2 = 8V

i2 = 490 mA

N1 = 600 Turns

N2 = N1* V2/V1

N2 = 600 * 8/120

N2 = 40 -----<<<<<Answer

-------------------------------

Power P = V2i2

P = 8 * 0.49

P = 3.92 Watts

-------------------------------------

Input Power P1 = V1i1

i1 = N2i2/N1

i1 = 40 * 0.49/600

i1 = 0.032 A

Input power P = V1i1

P = 120 * 0.032

e = p2/p1

P1 = P2/e

here effiiciency e = 100-15.5 = 84.5 %

so P1 = 3.92/0.845

P1 = 4.64 Watts

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