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NEETPhysicsAlternating Current

A coil is connected to a 10 V DC supply and draws a steady current of 0.5 A . When the same coil is connected to an AC source of 10 V and angular frequency 100 rad s ⁻¹ , it draws an rms current of 0.4 A . The inductance of the coil is

Options

  1. A0.05 H
  2. B0.25 H
  3. C0.15 H
  4. D15 H

Correct answer

C. 0.15 H

Step-by-step solution

For the DC supply, the coil acts as a pure resistor. Resistance R = V I_ DC = 10 0.5 = 20 For the AC supply, the coil acts as a series LR circuit. Impedance Z = V I_ AC = 10 0.4 = 25 The inductive reactance is given by X_L = Z^2 - R^2 X_L = 25^2 - 20^2 = 625 - 400 = 225 = 15 Since X_L = L , the inductance is: L = X_L = 15 100 = 0.15 H Answer: 0.15 H

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