Addition of __________ to the steel helps in increasing the residual magnetism in steel used for making magnets.

Residual magnetism in steel for magnets is increased by the addition of

A

Nickel

B

Cobalt

C

Tungsten

D

Chromium

The alloying element which increases residual magnetism and coercive magnetic force in steel for magnets is

A

Chromium

B

Nickel

C

Vanadium

D

Cobalt

Which one of the following phrases best describes residual magnetism?

A

Magnetism that remains in the core of an electromagnet after the current through the coil is turned off

B

The force of attraction between the poles of a permanent and temporary magnetic field

C

The amount of magnetic flux that is not confined to the core material of an electromagnet

D

The circular magnetic field that surrounds a conductor carrying a current

E

None of the above

Which of the following D.C. generators will be in a position to build up without any residual magnetism in the poles ?

A

Series generator

B

Shunt generator

C

Compound generator

D

None of the above

Following D.C. generator will be in a position to build up without any residual magnetism in the poles

A

Series generator

B

Shunt generator

C

Compound generator

D

Self-excited generator

In D.C. machines the residual magnetism is of the order of

A

2 to 3 percent

B

10 to 15 percent

C

20 to 25 percent

D

50 to 75 percent

If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be

A

Zero

B

Small

C

The same as rated voltage

D

High

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

Materials used for making permanent magnets containing iron and nickel are made by __________ technique.

A

Powder metallurgy

B

Casting

C

Forging

D

None of these

A company owns some land and buildings for which the following details are relevant : Cost of land Taka 50,000; cost of building Taka 100,000, estimated life of building 20 years, estimated residual value of building Taka 2000; estimated residual value of land Taka 50,000. The company uses the straight line depreciation method. Which is the correct annual depreciation charge for this asset?

A

Taka 4000

B

Taka 4900

C

Taka 7400

D

Taka 7500

Addition of __________ to the steel helps in increasing the residual magnetism in steel used for making magnets.

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