Question

A coil of inductance 300 mH and resistance 2Ω is connected to a source of voltage 2 V. The current reaches half of its steady state value in

• A. 0.1 s
• B. 0.05 s
• C. 0.3 s
• D. 0.15 s

Hint:

RL circuit current growth: I = I₀(1-e⁻t/τ)

Answer 1

The Correct Option is B

Step 1: Time constant τ = (L)/(R) = (0.3)/(2) = 0.15s
Step 2: (I)/(I₀) = 1 - e⁻t/τ
Step 3: For I = (I₀)/(2): t = τ ln 2 ≈ 0.05s