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

The residual magnetism of a self excited DC generator is lost. To build up its emf what to be done to regain the residual magnetism?

A

The field winding must be excited by double the rated DC voltage

B

The armature connection must be reversed

C

The field winding connection must be reversed

D

Field winding must be excited by low voltage DC supply

Consider the following statements The equivalent emf is equal to the individual emf of the cells in the series combination of cells having the same emf. The equivalent emf is equal to the individual emf of the cells in the parallel combination of cells having the same emf. Which of the following statement is correct?

A

Only 1

B

Only 2

C

Both 1 and 2

D

Neither 1 and 2

In DC machines the residual magnetism is present. The order of residual magnetism is ___________

A

2 to 3 per cent

B

10 to 15 per cent

C

20 to 25 per cent

D

50 to 75 per cent

What is the distance covered by boat N upstream in 5 hours? Which of the following option is sufficient alone to find the answer? A) Boat M is travelling downstream with 20% more downstream speed of boat N. Speed of boat M in still water is 10% more than the speed of boat N in still water. B) Boat M and Boat N are travelling downstream with speed 33 km/hr and 40 km/hr respectively and speed of boat M is still water is 2 times the speed of stream. C) Speed of boat M in still water is 6 km/hr less then speed of boat N in still water and speed of stream is 10 km/hr. D) Speed of stream is ½ times the speed of boat N in still water and downstream speed of boat M is 44 km/hr. E) Speed of stream is 10 km/hr and ratio of upstream speed of boat M and boat N is 3 : 2 respectively.

A

Only A and B

B

Only B and C

C

Only B

D

All A, B, C and D

E

None of A, B, C and D

In the circuit given below, what is the current flowing in 6Ω resistances?
Electricity and Magnetism mcq question image

A

0.22

B

0.55 A

C

2.22 A

D

2.775 A

The symbol represents.
Electricity and Magnetism mcq question image

A

unconnected wire crossing

B

a voltmeter

C

variable resistance or current controller

D

a resistance of resistance R

Use of signal in an electrical circuit. It is indicated by . . . . . . . .?

A

Rheostat

B

Resistor

C

Wire joint

D

Electric cell

What do the given symbol in figure represents in a reference of electric circuit?
Electricity and Magnetism mcq question image

A

resistance

B

plug key

C

electric bulb

D

battery

The given symbol stands for a/an . . . . . . . . in an electric circuit.
Electricity and Magnetism mcq question image

A

plug key

B

electric bulb

C

battery

D

resistor

The flow of . . . . . . . . is anti-clockwise in the given circuit.
Electricity and Magnetism mcq question image

A

resistance

B

voltage

C

electrons

D

current

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

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