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PHY 102 Electromagnetic Induction Objective Question
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Question

Why is the starting current of a DC motor much higher than its operating current?
Options
A Because the armature has higher resistance when cold
B Because back emf is zero at start, so I_start = V/R is large
Correct Answer
C Because the magnetic field is weaker at start
D Because the power supply delivers more voltage at start
Correct Answer

Option B is the correct answer.

Detailed Explanation

At start, the armature is not rotating, so back emf = 0. The current is then I = V/R (only armature resistance), which is much larger than the running current where back emf opposes V.

Hint

No back emf initially.

Question Info

Course: PHY 102
Topic: Electromagnetic Induction
Type: Objective
Difficulty: Not specified
Question 24 of 1819
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