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The magnetic field inside a 200 turns solenoid of radius 10 cm is 2.9×10⁻⁴ Tesla. If the solenoid carries a current of 0.29 A, then the length of the solenoid is ______ π cm.

Asked in JEE Main 29th Jan 2nd Shift 2025 · Solenoid, toroid and field energy

Answer: 8

Step-by-step solution

B=(μ₀ N I)/l, so l=(μ₀ N I)/B (radius not needed).

l=(4π×10⁻⁷×200×0.29)/(2.9×10⁻⁴)=0.08π m=8π cm

→ 8

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