A motor has an internal resistance of 12.0 Ω.When running,the motor has a back emf of 29 V and draws a current of 3.7 A.What is the supply voltage in this case?
A)29 V
B)44 V
C)73 V
D)15 V
E)32 V

Question

Quizplus · Accepted Answer

The supply voltage can be found using Ohm's law: 
supply voltage = (back emf) + (current drawn x internal resistance)
supply voltage = 29 V + (3.7 A x 12.0 Ω)
supply voltage = 29 V + 44.4 V
supply voltage = 73.4 V
Therefore, the best choice is (C) 73 V.

A Motor Has an Internal Resistance of 12