Electromagnetic Induction Test

Result

Electromagnetic Induction Test - 42

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Question 1
4 / -1

The number of turns in the coil of an ac generator is 5000 and the area of the coil is 0.25 m². The coil is rotated at the rate of 100 cycles/sec in a magnetic field of 0.2 W/m². The peak value of the e.m.f. generated is nearly

A
786 kV

B
440 kV

C
220 kV

D
157.1 kV

Solution
Question 2
4 / -1

In a dc motor, induced e.m.f. will be maximum

A
When motor takes maximum speed

B
When motor starts rotating

C
When speed of motor increases

D
When motor is switched off

Solution
Question 3
4 / -1

Work of electric motor is

A
To convert ac into dc

B
To convert dc into ac

C
Both (a) and (b)

D
To convert ac into mechanical work
Question 4
4 / -1

In an induction coil with resistance, the induced e.m.f. will be maximum when

A
The switch is put on due to high resistance

B
The switch is put off due to high resistance

C
The switch is put on due to low resistance

D
The switch is put off due to low resistance
Question 5
4 / -1

The induction coil works on the principle of

A
Self-induction

B
Mutual induction

C
Ampere's rule

D
Fleming's right hand rule
Question 6
4 / -1

An electric motor operates on a 50 volt supply and a current of 12A. If the efficiency of the motor is 30%, what is the resistance of the winding of the motor

A
6 Ω

B
4 Ω

C
2.9 Ω

D
3.1 Ω

Solution
Question 7
4 / -1

A motor having an armature of resistance 2 Ω is designed to operate at 220 V mains. At full speed, it develops a back e.m.f. of 210 V. When the motor is running at full speed, the current in the armature is

A
5 A

B
105 A

C
110 A

D
215 A

Solution
Question 8
4 / -1

A transformer is employed to

A
Obtain a suitable dc voltage

B
Convert dc into ac

C
Obtain a suitable ac voltage

D
Convert ac into dc
Question 9
4 / -1

What is increased in step-down transformer?

A
Voltage

B
Current

C
Power

D
Current density

Solution
Question 10
4 / -1

In a transformer 220 ac voltage is increased to 2200 volts. If the number of turns in the secondary are 2000, then the number of turns in the primary will be

A
200

B
100

C
50

D
20

Solution