Magnetic Effects & Magnetism

JEE Main level, single correct, medium

105 of 276

Question 105 of 276

If in a circular coil AA of radius RR, current I is flowing and in another coil BB of radius 2R2 R a current 2l2 \mathrm{l} is flowing, then the ratio of the magnetic fields BA\mathrm{B}_{\mathrm{A}} and BB\mathrm{B}_{\mathrm{B}}, produced by them will be

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Answer: (A) 1

In coil A, B =μ04π2πIR.∴BαIR=\frac{\mu_0}{4 \pi} \frac{2 \pi \mathrm{I}}{\mathrm{R}} . \quad \therefore \mathrm{B} \alpha \frac{\mathrm{I}}{\mathrm{R}}; Hence, B1 B2=I1R1⋅R2I2=22=1\frac{\mathrm{B}_1}{\mathrm{~B}_2}=\frac{\mathrm{I}_1}{\mathrm{R}_1} \cdot \frac{\mathrm{R}_2}{\mathrm{I}_2}=\frac{2}{2}=1

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