An induced emf is produced when a magnet is plunged into a coil. The magnitude of the induced emf is independent of
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → the resistivity of the wire of the coil
By Faraday's law the induced emf in a coil of \( N \) turns is
\( \displaystyle \varepsilon = -N\,\frac{d\Phi}{dt} \)
The emf depends only on the number of turns and on how fast the magnetic flux through each turn changes. The material of the wire does not appear; its resistance only decides how large the induced current \( I = \varepsilon/R \) is.
Option (3) the resistivity of the wire of the coil — Correct. The resistivity changes the resistance of the coil and hence the current, but not the emf.
NCERT (2026-27):
Faraday’s Law of Induction – “… The magnitude of the induced emf in a circuit is equal to the time rate of change of magnetic flux through the circuit. Mathematically, the induced emf is given by
\( \displaystyle \varepsilon = -\frac{d\Phi_B}{dt} \qquad (6.3) \)
… In the case of a closely wound coil of N turns, change of flux associated with each turn, is the same. Therefore, the expression for the total induced emf is given by
\( \displaystyle \varepsilon = -N\frac{d\Phi_B}{dt} \qquad (6.4) \)
The induced emf can be increased by increasing the number of turns N of a closed coil.”