Question

The reactance of an induction coil of 4 H for a dc current (in \( \Omega \)) is:

• A. zero
• B. \( 4\pi \)
• C. \( 40\pi \)
• D. \( 400\pi \)
• E. infinity

Hint:

For DC current, the inductive reactance is always zero because the frequency of DC current is zero. The reactance depends on the frequency of the AC current.

Answer 1

The Correct Option is A

The reactance \( X_L \) of an inductive coil is given by the formula: \[ X_L = 2\pi f L \] Where: - \( f \) is the frequency of the alternating current,
- \( L \) is the inductance of the coil.
For a DC current, the frequency \( f = 0 \) (because DC current has zero frequency).
Hence, the reactance \( X_L \) for a DC current becomes: \[ X_L = 2\pi \times 0 \times L = 0 \] Therefore, the reactance of the induction coil for a DC current is zero.