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A solenoid of length 0.5 m has a radius of 1 cm and is made up of 500 turns. It carries a current of 6 A. What is the magnitude of the magnetic field inside the solenoid ?

Asked in GSEB Board August 2020 · Solenoid, toroid and field energy

• (1) 24π×10⁻⁴ T
• (2) 20π×10⁻⁴ T
• (3) zero
• (4) 24π×10⁻⁴ G

Step-by-step solution

Why the other options are wrong

• (2) 20π×10⁻⁴ T needs nI=5×10⁵, that is a current of 5 A. This solenoid carries 6 A.
• (3) Zero is the field OUTSIDE an ideal long solenoid. Inside, the field is uniform and equal to μ₀ nI.
• (4) The right number in the wrong unit: 1 T=10⁴ G, so this is ten thousand times smaller than the field found.

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