A long solenoid of radius 1 mm has 100 turns per mm. A current of 1 A flows through it. Find the magnetic-field strength at its centre.
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A long solenoid of radius 1 mm has 100 turns per mm. A current of 1 A flows through it. Find the magnetic-field strength at its centre.

G1 Physics · Accepted Answer

Step 1: Solenoid's internal field is B=μ₀nI for long ideal solenoid. Step 2: Turns density n=100 turns/mm = 100/(10⁻³m)=10⁵m⁻¹. Step 3: B=4π×10⁻⁷×10⁵×1=4π×10⁻²T≈0.1257T. Answer B (12.56×10⁻²T). Final answer: (B) 12.56 × 10⁻² T.