A step-up transformer is designed to have an output voltage of 2 200 V (rms) whe

Question

A step-up transformer is designed to have an output voltage of 2 200 V (rms) when the primary is connected across a 110-V (rms) source.

(a) If the primary winding has exactly 82 turns, how many turns are required on the secondary?
turns

(b) If a load resistor across the secondary draws a current of 1.00 A, what is the current in the primary, assuming ideal conditions?
A

(c) If the transformer actually has an efficiency of 97.0%, what is the current in the primary when the secondary current is 1.20 A?

Explanation / Answer

A) E1/E2 = N1/N2..

N2 = N1*(E2/E1) = 82*(2200/110) = 1640 turns

B) for ideal tranformer
E1*I1 = E2*I2

I1 = E2*I2/E1 = (2200*1)/110 = 20 A

C) efficiency e= (E2*I2)*100/(E1*I1) .....
97/100 = (2200*1.2)/(110*I1)...

I1 = (2200*1.2)/(110*0.97) = 24.74 A

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