Free Printable Electrical Machines 1

1.

how will you find the magnetic field strength?

a)

$B=\phi\div A$

b)

$E=\frac{\text{d}\phi}{\text{dt}}$

c)

$H=\frac{MMF}{L}$

d)

$MMM=NI$

2.

how will you find the magnetic flux density?

a)

$B=\phi\div A$

b)

$E=\frac{\text{d}\phi}{\text{dt}}$

c)

$H=\frac{MMF}{L}$

d)

$MMM=NI$

3.

write the formula for finding emf induced in the coil?

a)

$B=\phi\div A$

b)

$E=\frac{\text{d}\phi}{\text{dt}}$

c)

$H=\frac{MMF}{L}$

d)

$MMM=NI$

4.

write the unit of magnetic flux?

a)

$\frac{wb}{m^2}$

b)

wb

c)

AT

d)

AT/m

5.

write the unit of magnetic flux density?

a)

$\frac{wb}{m^2}$

b)

wb

c)

AT

d)

AT/m

6.

write the unit of magnetic field intensity?

a)

$\frac{wb}{m^2}$

b)

wb

c)

AT

d)

AT/m

7.

write the unit of magneto motive force (mmf)?

a)

$\frac{wb}{m^2}$

b)

wb

c)

AT

d)

AT/m

8.

write the formula for finding mmf?

a)

$B=\phi\div A$

b)

$E=\frac{\text{d}\phi}{\text{dt}}$

c)

$H=\frac{MMF}{L}$

d)

$mmf=NI$

9.

According to Lenz law write the formula for finding emf induced in the coil?

a)

$B=\phi\div A$

b)

$E=-\frac{\text{d}\phi}{\text{dt}}$

c)

$H=\frac{MMF}{L}$

d)

$MMM=NI$

10.

What is a simple machine?

a)

a device that has only one working motor

b)

a device that makes work easier

c)

a device that makes more work for a job

d)

device that is made up of two or more machines

11.

Which is the device in DC Generators that converts AC current into DC current

a)

brushes

b)

commutator

c)

stator

d)

armature

12.

DC Generators give

a)

mechanical energy

b)

Electrical energy

c)

DC Electrical energy

d)

AC Electrical energy

13.

Which of these is NOT a part of a DC Generator.

a)

Slip rings

b)

commutator

c)

brushes

d)

stator

14.

Figure shown is an Industrial DC Generator. What does the label ″W″ indicate.

a)

Armature

b)

Field coil

c)

brushes

d)

commutator

15.

Which is the device in DC Generators that converts AC current into DC current

a)

brushes

b)

commutator

c)

stator

d)

armature

16.

In separately excited field generators, the stator produces its magnetic field

a)

by external source of dc current

b)

by current from armature

c)

by permanent magnets

17.

In self excited field generators, the stator strengthens its magnetic field

a)

by external source of dc current

b)

By current from armature

c)

By permanent magnet

18.

In the Flemming's left hand rule, the thumb is representing the ....

a)

Direction of magnetic field

b)

Direction of electric current

c)

Motion of wire

d)

Turning effect of coil

19.

Which part (s) of the DC motor connect the power supply to the split-ring and coil?

a)

Carbon brushes

b)

Magnets

c)

Commutator

d)

Slip rings

20.

What is the name of the effect caused by the wire when it is moved across a magnetic field?

a)

Induced magnetism

b)

Electromagnetic induction

c)

Electromagnetism

d)

Turning effect of coil

21.

Generators get their mechanical power from

a)

Batteries

b)

Prime mover

c)

Transistor

d)

Capacitors

22.

D.C. generators are installed near the load centres to reduce

a)

iron losses

b)

line losses

c)

sparking

d)

corona losses

23.

D.C. generators are normally designed for maximum efficiency around

a)

full-load

b)

rated r.p.m.

c)

rated voltage

d)

all of the above

24.

In a D.C. generator all of the following could be the effects of iron losses except

a)

Loss of efficiency

b)

Excessive heating of core

c)

Increase in terminal voltage

d)

Rise in temperature of ventilating air

25.

In a D.C. generator, the iron losses mainly take place in

a)

yoke

b)

commutator

c)

armature conductors

d)

armature rotor

26.

Which of the following loss in a D.C. generator varies significantly with the load current ?

a)

Field copper loss

b)

Windage loss

c)

Armature copper loss

d)

None of the above

27.

Which of the following losses are significantly reduced by laminating the core of a D.C. generator ?

a)

Hysteresis losses

b)

Eddy current losses

c)

Copper losses

d)

Windage losses

28.

Which one of the following is not the function of pole shoes in a D.C. machine ?

a)

To reduce eddy current loss

b)

To support the field coils

c)

To spread out flux for better uniformity

d)

To reduce the reluctance of the magnetic path

29.

An electro-mechanical energy conversion device is one which converts _______

a)

Electrical energy to mechanical energy only

b)

Mechanical energy to electrical energy only

c)

All of the mentioned

d)

None of the mentioned

30.

For a linear electromagnetic circuit, which of the following statement is true?

a)

Field energy is less than the Co-energy

b)

Field energy is equal to the Co-energy

c)

Field energy is greater than the Co-energy

d)

Co-energy is zero

31.

The energy stored in a magnetic field is given by ____________ where L=self-inductance and Rl=reluctance.

a)

1/2 Li2

b)

1/2 (mmf*Rl)2

c)

1/2∅Rl

d)

1/2 φ2i

32.

A device that uses electricity.

a)

Load

b)

Battery Source

c)

Energy pathway

33.

If a unit positive charge is taken from one point to another over an equipotential surface, then

a)

Work is done on the charge

b)

Work is done by the charge

c)

Work done is constant

d)

No work is done

34.

Surrounding every magnet is a __________ __________.

a)

magnetic field

b)

electrical current

c)

another magnet

d)

an enemy

35.

What two forces are required for generators and electric motors to work?

a)

magnetism and thermal

b)

electricity and thermal

c)

electricity and magnetism

d)

magnetism and radiant

36.

Electricity is the flow of _________.

a)

Protons

b)

Neutrons

c)

Electrons

37.

How are electromagnets different from magnets?

a)

magnets can be turned on/off

b)

you can turn an electromagnet on/off

c)

magnets are more powerful

d)

magnets have a North and South pole

38.

What happens to the strength of an electromagnet as you add more coils around it?

a)

Increases

b)

Decreases

c)

Stays the same

d)

Stops completely

39.

True or False: A magnetic field is invisible.

a)

True

b)

False

40.

In D.C. machines fractional pitch winding is used

a)

to improve cooling

b)

to reduce copper losses

c)

to increase the generated e.m.f.

d)

to reduce the sparking

Electrical Machines 1

Total questions: 40

Worksheet time: 40mins

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