Electro Magnetic Induction And Alternating Currents Question 502

Question: A simple electric motor has an armature resistance of 1Ω  and runs from a dc source of 12 volt. When running unloaded it draws a current of 2 amp. When a certain load is connected, its speed becomes one-half of its unloaded value. What is the new value of current drawn?

Options:

A) 7 A

B) 3 A

C) 5 A

D) 4 A

Show Answer

Answer:

Correct Answer: A

Solution:

  • Let initial e.m.f. induced =e
    Initial current i=EeR i.e., 2=12e1

    This gives e=122=10 volt. As eω .

    when speed is halved, the value of induced e.m.f. becomes e2=102=5,volt
    New value of current i=EeR=1251=7A



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