Magnetic Effects & Magnetism

JEE Main level, single correct, medium

103 of 276

Question 103 of 276

A long wire carries a steady current. It is bent into a circle of one turn and the magnetic field at the centre of the coil is BB. It is then bent into a circular loop of nn turns. The magnetic field at the centre of the coil will be

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Answer: (B) n2 B\mathrm{n}^2 \mathrm{~B}

B′=πμ0I2r′=n2μ0ππℓ=n2BB^{\prime}=\frac{\pi \mu_0 I}{2 r^{\prime}}=n^2 \frac{\mu_0 \pi \pi}{\ell}=n^2 B.

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