# Electromagnetic Induction & Alternating Currents (NEET Physics): Questions 47 - 50 of 124

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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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