If a coil made of conducting wires is rotated between the pole pieces of a permanent magnet,the motion will generate a current. This device is called:

Armature current in a $DC$ motor will be maximum when:

The output of a dynamo using a split-ring commutator is

The armature of a $DC$ motor has $20\,\Omega$ resistance. It draws a current of $1.5\,A$ when run by a $220\,V$ $DC$ supply. The value of the back $EMF$ induced in it will be......$V$

$A$ rectangular coil of a simple $A.C.$ generator rotates about one of its diameters with a constant angular frequency in the presence of a uniform magnetic field. The direction of the induced current reverses for the third time after how many rotations of the coil?

$A$ generator has an armature resistance of $0.1 \, \Omega$ and develops an induced emf of $120 \, V$ when driven at its rated speed. Its terminal voltage when a current of $50 \, A$ is being drawn is ................. $V$.