Electromagnetic Induction & Alternating Currents (NEET Physics): Questions 47 - 50 of 121

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Question number: 47

» Electromagnetic Induction & Alternating Currents » Reactance and Impedance

MCQ▾

Question

A 20 volt ac is applied to a circuit consisting of a resistance and a coil with negligible resistance. If the voltage across the resistance is 12 V, the voltage across the coil is

Choices

Choice (4) Response

a.

6 volt

b.

16 volt

c.

8 volt

d.

10 volt

Question number: 48

» Electromagnetic Induction & Alternating Currents » Self and Mutual Inductance

MCQ▾

Question

A current of 10 A in the primary coil of a circuit is reduced to zero at a uniform rate in 10 -3 second. If the coefficient of mutual inductance is 3H, the induced e. m. f. in the secondary coil will be,

Choices

Choice (4) Response

a.

3 kV

b.

2 kV

c.

30 kV

d.

20kV

Question number: 49

» Electromagnetic Induction & Alternating Currents » AC Generator and Transformer

Assertion-Reason▾

Assertion (Ꭺ)

An electric motor will have maximum efficiency when back e. m. f. is equal to half of the applied e. m. f.

Reason (Ꭱ)

Efficiency of electric motor depends only on magnitude of back e. m. f.

Choices

Choice (4) Response

a.

Both Ꭺ and Ꭱ are false

b.

Both Ꭺ and Ꭱ are true but Ꭱ is NOT the correct explanation of Ꭺ

c.

Both Ꭺ and Ꭱ are true and Ꭱ is the correct explanation of Ꭺ

d.

Ꭺ is true but Ꭱ is false

Question number: 50

» Electromagnetic Induction & Alternating Currents » Induced EMF and Current

MCQ▾

Question

5.5 x 10 -4 magnetic flux lines are passing through a coil of resistance 10 ohm and number of turns 1000. If the number of flux lines reduces to 5 x 10 -5 in 0.1 sec. Then

(1) The electromotive force induced in the coil is 5V

(2) The electromotive force induced in the coil is 5 x 10 -4 V

(3) The current induced in the coil is 0.5 A

(4) The current induced in the coil is 10 A

Select the correct answers and mark it according to the following codes:

Choices

Choice (4) Response

a.

1 and 3 are correct

b.

1, 2 and 3 are correct

c.

2 and 4 are correct

d.

1 and 2 are correct

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