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A solenoid of length 0.5 m has a radius of 1 cm and is made up of 1000 turns. It carries a current of 5 A. The magnitude of the magnetic field inside the solenoid is ______ T.

Asked in GSEB Board March 2022 · Solenoid, toroid and field energy

• (1) 3π×10⁻³
• (2) 2π×10⁻³
• (3) π×10⁻³
• (4) 4π×10⁻³

Step-by-step solution

Why the other options are wrong

• (1) Needs nI=7.5×10³. Here n=2000 m⁻¹ and I=5 A, so nI=10⁴.
• (2) Half the answer: either (μ₀ nI)/2, which is the field at the END of a long solenoid rather than inside it, or 500 turns used instead of 1000.
• (3) A quarter of the answer; it needs nI=2.5×10³, for instance the 1000 turns spread over 2 m instead of 0.5 m.

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