Question:medium

A 50 Hz AC current of crest value 1 A flows through the primary of a transformer. If the mutual inductance between the primary and secondary is 0.5 H, the crest voltage induced in the secondary is______.
Fill in the blank with the correct answer from the options given below.

Updated On: May 17, 2026
  • 75 V
  • 150 V
  • 100 V
  • 200 V
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The Correct Option is B

Solution and Explanation

Analysis of induced voltage in the transformer's secondary coil.

1. Induced Voltage (εs):

The formula for the induced voltage in the secondary coil is:

εs = M(dIp/dt)

Where:

  • M = mutual inductance
  • Ip = primary coil current
  • t = time

2. Primary Current (Ip):

The primary current is defined as:

Ip = I0sin(ωt)

Where:

  • I0 = peak current (1 A)
  • ω = angular frequency (ω = 2πf)
  • f = frequency (50 Hz)

Substituting the values:

Ip = 1 * sin(2π * 50 * t)

Ip = sin(100πt)

3. Rate of Change of Primary Current (dIp/dt):

The derivative of the primary current with respect to time is:

dIp/dt = d(sin(100πt))/dt

dIp/dt = 100πcos(100πt)

4. Induced Voltage (εs):

Substituting the rate of change of current into the induced voltage formula:

εs = M(dIp/dt)

εs = 0.5 H * 100πcos(100πt)

εs = 50πcos(100πt)

5. Crest Voltage (ε0):

The maximum induced voltage (crest voltage) occurs when cos(100πt) = 1:

ε0 = 50π V

Using π ≈ 3.14:

ε0 = 50 * 3.14 V

ε0 = 157 V

The calculated crest voltage induced in the secondary coil is approximately 157 V.

The closest available answer is 150 V.

The correct answer is:

Option 2: 150 V

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