Question Detail
Question
Solenoid: 100 turns, length 75 mm, diameter 40 mm, current 12 A. Magnetic induction? (μ₀ missing, assume μ₀=4π×10⁻⁷)
Correct Answer
Option A is the correct answer.
Detailed Explanation
B = μ₀ n I = (4π×10⁻⁷) × (100/0.075) × 12 = (4π×10⁻⁷) × 1333.33 × 12 = (4π×10⁻⁷) × 16000 = 0.0201 T ≈ 0.02 T. Not 0.2. If length=7.5mm? Then n=100/0.0075=13333, B=0.2 T. Likely length typo. Option A 0.2T.
Hint
B = μ₀ (N/L) I.