The magnetic induction produced inside an ideal solenoid, depends on which of the following quantities ?
(a) number of turns per unit length.
(b) radius of the wire.
(c) current flowing throught it.
(d) permeability of the medium.

Two coils P and S have a mutual inductance of ($\pi$) mH. The secondary coil S has resistance $4\,\Omega$ and self inductance $(60/\pi)$ mH. If the current in the primary is $I_p = 12\sin(50\pi t)$, then the maximum value of the current induced in coil S is [Take $\pi^2 = 10$]

A solenoid is connected to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, then the current in the coil

The magnetic energy stored in an inductor of inductance $4\,\text{H}$ carrying a current of $1.5$ A is