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Electromagnetic-theory Questions Set 75:

Quiz Mode

The total losses in a well-designed 10 kW D.C. generator will be approximately

100 W

500 W

1000 W

1500 W

Solution:

Calculate the magnetic moment when a magnetic field of B = 74 units is subjected to a torque of 24 units.

0.121

0.247

0.324

0.468

Solution:

The expression for the phase constant is given by

Phase constant β = ωμε

Phase constant ω = με

Phase constant β = ω√(με)

Phase constant β = 1/ωμε

Solution:

Which of the following law/rule can be used to determine the direction of rotation of a D.C. motor?

Lenz's law

Faraday's law

Coulomb's law

Fleming's left-hand rule

Solution:

What will happen if the back EMF (electromotive force) of a DC motor suddenly disappears?

The motor will stop

The motor will continue to run

The armature may burn

The motor will run noisily

Solution:

When a magnet is in motion relative to a coil, the induced electromotive force (EMF) does not depend on

pole strength of the magnet

number of turns of the coil

resistance of the coil

motion of the magnet

Solution:

If the impedance and resistance of a transmission line are 40Ω and 0.4Ω/m respectively, find the attenuation constant. Assume that the transmission line is distortionless.

100 Np/m

0.01 Np/m

160 Np/m

16 Np/m

Solution:

In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to

(a) 100% of the previous value

(b) 50% of the previous value

(d) 10% of the previous value

Solution:

Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator?

(a) Providing laminations in armature core

(b) Providing laminations in stator

(d) Using material of low hysteresis coefficient for armature core material

Solution:

If an electron and a proton have the same momentum and enter a magnetic field perpendicularly, then

The curved paths of the electron and proton will be the same (ignoring the sense of revolution)

They will move undeflected

The curved part of the electron's path will be more curved than that of the proton

The path of the proton will be more curved

Electromagnetic-theory Questions Set 75:

The total losses in a well-designed 10 kW D.C. generator will be approximately

Solution:

Calculate the magnetic moment when a magnetic field of B = 74 units is subjected to a torque of 24 units.

Solution:

The expression for the phase constant is given by

Solution:

Which of the following law/rule can be used to determine the direction of rotation of a D.C. motor?

Solution:

What will happen if the back EMF (electromotive force) of a DC motor suddenly disappears?

Solution:

When a magnet is in motion relative to a coil, the induced electromotive force (EMF) does not depend on

Solution:

If the impedance and resistance of a transmission line are 40Ω and 0.4Ω/m respectively, find the attenuation constant. Assume that the transmission line is distortionless.

Solution:

In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to

Solution:

Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator?

Solution:

If an electron and a proton have the same momentum and enter a magnetic field perpendicularly, then

Solution:

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