Question

A transformer increases an alternating e.m.f. from 220V to 880V. If primary coil has 1000 turns, the number of turns in the secondary coil are .............

• A. 1000
• B. 2000
• C. 3000
• D. 4000

Hint:

For a step-up transformer, the voltage increases, so the number of turns in the secondary coil must be greater than in the primary. For a step-down, it's the opposite. Here, voltage increased 4 times, so turns must also increase 4 times.

Answer 1

The Correct Option is D

For an ideal transformer, the ratio of the secondary voltage (\(V_s\)) to the primary voltage (\(V_p\)) is equal to the ratio of the number of turns in the secondary coil (\(N_s\)) to the number of turns in the primary coil (\(N_p\)). \[ \frac{V_s}{V_p} = \frac{N_s}{N_p} \] Given:
Primary voltage, \(V_p = 220\) V
Secondary voltage, \(V_s = 880\) V
Number of turns in primary coil, \(N_p = 1000\)
Substituting the values: \[ \frac{880}{220} = \frac{N_s}{1000} \] \[ 4 = \frac{N_s}{1000} \] \[ N_s = 4 \times 1000 = 4000 \] The number of turns in the secondary coil is 4000.