Electromagnetic Induction Test

Result

Electromagnetic Induction Test - 68

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Weekly Quiz Competition

Question 1
4 / -1

Choke coil works on the principle of

A
Transient current

B
Self-induction

C
Mutual induction

D
Wattless current
Question 2
4 / -1

When the speed of a dc motor increases the armature current

A
Increases

B
Decreases

C
Does not change

D
Increases and decreases continuously

Solution
Question 3
4 / -1

A six pole generator with fixed field excitation develops an e.m.f. of 100 V, when operating at 1500 rpm. At what speed must it rotate to develop 120 V?

A
1200 rpm

B
1800 rpm

C
1500 rpm

D
400 rpm

Solution
Question 4
4 / -1

The coil of dynamo is rotating in a magnetic field. The developed induced e.m.f. changes and the number of magnetic lines of force also changes. Which of the following conditions is correct

A
Lines of force minimum but induced e.m.f. is zero

B
Lines of force maximum but induced e.m.f. is zero

C
Lines of force maximum but induced e.m.f. in not zero

D
Lines of force maximum but induced e.m.f. is also maximum

Solution
Question 5
4 / -1

Armature current in dc motor will be maximum when

A
Motor has acquired maximum speed

B
Motor has acquired intermediate speed

C
Motor has just started moving

D
Motor is switched off

Solution
Question 6
4 / -1

The armature of dc motor has 20 Ω resistance. It draws current of 1.5 ampere when run by 220 volts dc supply. The value of back e.m.f. induced in it will be

A
150 V

B
170 V

C
180 V

D
190 V

Solution
Question 7
4 / -1

A transformer with efficiency 80% works at 4 kW and 100 V. If the secondary voltage is 200 V, then the primary and secondary currents are respectively.

A
40 A, 16 A

B
16 A, 40 A

C
20 A, 40 A

D
40 A, 20 A

Solution
Question 8
4 / -1

Fan is based on

A
Electric motor

B
Electric dynamo

C
Both of (a) and (b)

D
None of these
Question 9
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 10
4 / -1

What is increased in step-down transformer

A
Voltage

B
Current

C
Power

D
Current density

Solution