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.

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?

An a.c. generator consists of a coil of 50 turns and area 2.5 m^(2) rotating att an angular speed of 60 rad s^(-1) in a uniform magnetic field B = 0.3 T between two fixed pole pieces. The resistance of the circuit including that of coil is 500 Omega . Find What will be the orientaiton of the coil w.r.t. the magnetic field to have (a) maximum (b) zero magnetic flux ?

An electric motor runs on a dc source of emf E and internal resistance r. Show that the power output of the source, is maximum when the current drawn by the motor is (E)/(2r) .

A flat coil of 500 turns each of area 50 cm^(2) rotates in a uniform magnetic field of 0.14 Wb//m^(2) at an angular speed of 150 rad//sec . The coil has a resistance of 5 Omega. The induced e.m.f. is applied to an external resistance of 10 ohm. Calculate the peak current through the resistance.

The back e.m.f. of a d.c. motor delivering 5 kW of mechanical power is 200 v, when operating on a 220 V line. Determine the armatre current and the motor resistsance.

A battery of e.m.f. 10V and internal resistance 3 Omega is connected to a resistor. If the current in the circuit is 0.5 A, What is the resistance of the resistor? What is the terminal voltage of the battery when the circuit is closed?