Question Detail
Question
A DC motor has armature resistance 2 Ω and draws 5 A at full speed when connected to 120 V. What is the back emf?
Correct Answer
Option B is the correct answer.
Detailed Explanation
Using V - ε_b = IR, 120 - ε_b = (5 A)(2 Ω) = 10 V, so ε_b = 120 - 10 = 110 V.
Hint
Back emf = V - IR.