_________ electromagnets generally function as holding magnets.

Which of the following is the commonly used type of electromagnets ?

A

Flat-faced armature type

B

Horse shoe type

C

Flat-faced plunger type

D

All of the above

The design of electromagnets is based upon which of the following fundamental equations ?

A

Force equation

B

Magnetic circuit equation

C

Heating equation

D

Voltage equation

E

All of the above

are used for construction of core of electromagnets.

A

Soft magnetic materials

B

Hard magnetic materials

C

Either (A) or (B)

D

None of the above

If a bar magnet is __, the two pieces form two complete magnets, each with north and south pole.

A

broken

B

broke

C

breaking

D

break

Permanent magnets are made of high carbon steel and

A

15% of cobalt

B

20% of cobalt

C

35% of cobalt

D

45% of cobalt

Those materials are well suited for making permanent magnets which have ________ retentivity and ________ coercivity.

A

Low, high

B

High, high

C

High, low

D

Low, low

Temporary magnets are used in

A

loud-speakers

B

generators

C

motors

D

all of the above

Permanent magnets are normally made of

A

Alnico alloys

B

Aluminium

C

Cast iron

D

Wrought iron

Hard steel is suitable for making permanent magnets because

A

It has good residual magnetism

B

Its hysteresis loop has large area

C

Its mechanical strength is high

D

Its mechanical strength is low

The use of permanent magnets is. not made in

A

magnetoes

B

energy meters

C

transformers

D

loud-speakers

_________ electromagnets generally function as holding magnets.

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