A coil A is connected to a voltmeter V and the other coil B to an alterniting current sourecs, Fig. If a large copper sheet is placed between the two coils, how does the induced emf in coil A change due to current in coil B ?

Explanation

In the source of copper sheet, emf will be induced in coil A due to mutual induction between the two coils A and B. Voltemter in coil A will show deflection as per the magnetude of emf induced.
When a copper sheet is placed between the two coils eddy currents are set up in the sheet due to change in magnetic flux linked with C. Magnetic flux linked with coil A, due to col B and due to opposing eddy currents in C will decrease. Therefore, rate of change of magnetic flux in A will decrease. Hence emf induced in A will decrease.