A rectangular coil having 200 turns and area 100 cm2 is placed in a uniform magnetic field 0.2 T with its plane perpendicular to the magnetic field. It is then flipped by 180° in 0.01 s. If the resistance of the material of the coil is 2 Ω, then the induced current in the coil is
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 40 A
By Faraday’s law, the average induced emf equals the change in flux linkage divided by the time taken. Flipping the coil by 180° reverses the flux, so the change is twice the initial flux.
\( \displaystyle A = 100\,\mathrm{cm^{2}} = 1\times10^{-2}\,\mathrm{m^{2}} \)
\( \displaystyle \Delta\Phi = NBA - (-NBA) = 2NBA \)
\( \displaystyle \Delta\Phi = 2 \times 200 \times 0.2\,\mathrm{T} \times 1\times10^{-2}\,\mathrm{m^{2}} = 0.8\,\mathrm{Wb} \)
\( \displaystyle \varepsilon = \frac{\Delta\Phi}{\Delta t} = \frac{0.8\,\mathrm{Wb}}{0.01\,\mathrm{s}} = 80\,\mathrm{V} \)
\( \displaystyle I = \frac{\varepsilon}{R} = \frac{80\,\mathrm{V}}{2\,\Omega} = 40\,\mathrm{A} \)
This is the average current during the flip.
Note: NTA picked this question from an NCERT (2026-27) example and changed the figures. Do not ignore NCERT while practising numericals.
NCERT (2026-27):
Faraday’s Law of Induction – …
