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Physics · PYQ NEET UG 2016(2)
हिन्दीA uniform magnetic field is restricted within a region of radius \( r \). The magnetic field changes with time at a rate \( \frac{dB}{dt} \). Loop 1 of radius \( R > r \) encloses the region \( r \) and loop 2 of radius \( R \) is outside the region of magnetic field. The induced e.m.f. generated is
Correct answer · Option 1
-\( \frac{dB}{dt} \pi r^2 \) in loop 1 and zero in loop 2
Explanation
Induced emf is given by \( \varepsilon = -\frac{d\Phi_B}{dt} = -A \frac{dB}{dt} \). For loop 1, the effective area enclosing the magnetic field is \( \pi r^2 \), giving an emf of -\( \frac{dB}{dt} \pi r^2 \). For loop 2, the enclosed magnetic flux is zero as it lies outside the field region, resulting in zero emf.
