A pair of adjacent coils has a mutual inductance of 2.0 H. If the current in one coil changes from 0 to 25 A in 0.8 s, the change of flux linkage with the other coil is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 50 Wb
By the definition of mutual inductance, the flux linked with the second coil is proportional to the current in the first: \( N\Phi = M I \). So the change of flux linkage depends only on the change of current, not on the time taken.
\( \displaystyle \Delta(N\Phi) = M\,\Delta I = 2.0\,\mathrm{H} \times (25 - 0)\,\mathrm{A} = 50\,\mathrm{Wb} \)
The time 0.8 s is needed only for the induced emf, \( |\varepsilon| = M\,\Delta I/\Delta t = 62.5\,\mathrm{V} \).
Note: NTA picked this question from an NCERT (2026-27) exercise and changed the figures. Do not ignore NCERT while practising numericals.
NCERT (2026-27):
Exercises – …
