Electromagnetic Induction

Wires $AB$ and $CD$ are parallel to each other, as shown. Wire $AB$ contains a battery and a switch $S$; wire $CD$ contains a galvanometer $G$. Initially the switch is open.

In the circuit shown, a central primary coil is connected to a battery through a rheostat $R$. On either side sit two secondary coils, $A$ (left) and $B$ (right), each closed through a galvanometer $G$. The sliding contact of $R$ is moved to the left so that the current in the primary coil is weakened.

A bar magnet is pushed into a closed solenoid from its right end and pulled out from its left end, so the magnet moves steadily to the left all the way through the coil.

A primary coil carrying a battery and a switch $S$, and a secondary coil connected to a resistor $R$, are wound on the same core. Consider the current through $R$ in each of the following cases.

A movable conducting wire slides to the right with velocity $v$ along a rectangular circuit. A magnetic field is present in region $A$, to the left of the wire. As the wire moves, the induced current it produces is directed upward in the wire (as shown).