(A) 100 m/s
(B) 450 m/s
(C) 200 m/s
(D) 900 m/s
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If the emf induced in a coil is 200 V when the current changes from 1 a to 2 A in 0.05s , the self-inductance of the coil is:
(A) 1 H
(B) 10 H
(C) 20 H
(D) 30 H
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A step-up transformer is used on a 120 V line to provide a potential difference of 2400 V. If the primary coil has 75 turns, the number of turns in the secondary coil is:
(A) 1500
(B) 1200
(C) 150
(D) 1575
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In a step-up transformer, the turns ratio of primary and secondary is 1:2. A Laclanche cell of emf 1.5 V is connected across the primary. The voltage developed across the secondary would be:
(A) zero
(B) 3.0 V
(C) 1.5 V
(D) 0.75 V
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The current passing through a choke coil of 5 H is decreasing at the rate of 2 A/s. The emf developed across the coil is:
(A) 10 V
(B) -10 V
(C) 2.5 V
(D) -2.5 V
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An ideal transfer is used to step up an alternating emf of 220 V to 4.4 kV to transmit 6.6 kW of power. The current rating of the secondary is:
(A) 30 A
(B) 3 A
(C) 1.5 A
(D) 1 A
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To induce an emf in a coil, the linking magnetic flux:
(A) must decrease
(B) must increase
(C) must remain constant
(D) can either increase or decrease
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The direction of induced emf during electromagnetic induction is given by:
(A) Faraday’s law
(B) Lenz’s law
(C) Maxwell’s law
(D) Ampere’s law
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The self-inductance of a coil is 5 h. A current of 1 A changes to 2 A within 5 s through the coil. The value of induced emf will be:
(A) 10 V
(B) 0.1 V
(C) 1.0 V
(D) 100 V