An electric motor operating at 200 V draws a current of 5 A at its full speed. The resistance of the armature is `10 Omega`. Calculate the back e.m.f. and efficiency of the motor?

A small d.c. motor operating at 200 V draws a current of 5.0 A at its full speed of 3,000 r.p.m. The resistance of the armature of the motor is 8.5 Omega. Determine the back e.m.f. of the motor. Obtain the power input, power output (mechanical) and the efficiency of the motor.

When a motor is at its full speed, a lesser current flows through the arature. Why?

A storage battery of a car has an e.m.f. of 12V. If the internal resistance of the battery is 0.4 Omega , what is the maximum current that can be drawn from the battery?

An alternating e.m.f of 100 V(r.m.s) 50 Hz is applied across a capacitor of 10muF and a resistance of 100 ohm in series. Calculate the reactance of the capacitor.

Now assume that the straight wire carries a current of 50 A and a loop is moved to the right with a constant velocity, v = 10ms^-1 . Calculate the induced e.m.f. in the loop at the instant when x = 0.2 m. Take a = 0.1 m and assume that the loop has a large resistance.