A coil is wound on a core of rectangular crosssection. If all the linear dimensions of core are increased by a factor 3 and number of turns per unit length of coil remains same, the selfinductance increases by a factor

What is the phase difference between the flux linked with a coil rotating in a uniform magnetic field and the induced e.m.f. produced in it?

Two coils $P$ and $Q$ are kept near each other. When no current flows through coil $P$ and current increases in coil Q at the rate of $10 \mathrm{~A} / \mathrm{S}$, the e.m.f. in coil P is 15 mV . When coil Q carries no current and current of 1.8 A flows through coil $P$, the magnetic flux linked with coil Q is