# Question: a dc motor a shuntwound dc motor with the field...

###### Question details

**A DC Motor**

A shunt-wound DC motor with the field coils and rotor connected
in parallel (see the figure) (Figure 1) operates from a 115 V DC
power line. The resistance of the field windings, *R*f, is
205 Ω . The resistance of the rotor, *R*r, is 6.00 Ω . When
the motor is running, the rotor develops an emf E. The motor draws
a current of 4.20 A from the line. Friction losses amount to 49.0 W
.

**Part A**

Compute the field current *I*f.

**Part B**

Compute the rotor current *I*r.

**Part C**

Compute the emf E.

**Part D**

Compute the rate of development of thermal energy in the field windings.

**Part E**

Compute the rate *P*th,rotor of development of thermal
energy in the rotor.

**Part F**

Compute the power input to the motor *P*in.

**Part G**

Compute the efficiency of the motor.