Owen Ryan Ang
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Engineering Quiz on ELECTROMAGNETIC INDUCTION, created by Owen Ryan Ang on 24/01/2020.

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Owen Ryan Ang
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ELECTROMAGNETIC INDUCTION

Question 1 of 36

1

The coefficient of self-inductance of a coil is defined as

Select one of the following:

  • NI/Φ

  • NΦ/I

  • Φ/NI

  • ΦI/N

Explanation

Question 2 of 36

1

Which of the following statement is incorrect?

Select one of the following:

  • Whenever the flux linking with the coil or circuit changes the emf is produced.

  • The direction of dynamically induced emf can be determined by Flemming's right hand rule.

  • Coefficient of coupling for tightly coupled coil is zero.

  • The coefficient of self-inductance is proportional to the square of number of turns on it.

Explanation

Question 3 of 36

1

Which of the following statements about inductance of a coil is true?

Select one of the following:

  • Inductance is a characteristic of coil occurring only in case of A.C.

  • Inductance appears only if the coil has an iron core.

  • Inductance is only another expression for self-induced voltage.

  • Inductance characterizes the magnetic properties of a coil which are significant for the value of self-induced voltage generated due to current change in the coil.

Explanation

Question 4 of 36

1

A collapsing field around a coil

Select one of the following:

  • tends to oppose the decay of coil current

  • helps the decay of coil current

  • tends to aid current flow reversal

  • does not affect the coil current flow

Explanation

Question 5 of 36

1

Energy stores in an inductance is given by

Select one of the following:

  • 2LI2 joules

  • 0 joule

  • NΦ/I joules

  • 1/2 LI2 joules

Explanation

Question 6 of 36

1

Which of the following is a vector quantity?

Select one of the following:

  • magnetic potential

  • flux density

  • magnetic field intensity

  • relative permeability

Explanation

Question 7 of 36

1

A conductor of length L has current I passing through it, when it is placed parallel to a strong magnetic field. The force experience by the conductor will be

Select one of the following:

  • BLI

  • zero

  • B2LI

  • BL2I

Explanation

Question 8 of 36

1

Whenever a conductor cuts magnetic flux, an emf is induced in that conductor. This statement is due to

Select one of the following:

  • Joule's law

  • Coulomb's law

  • Faraday's law

  • Weber and Ewing's theory

Explanation

Question 9 of 36

1

The left hand rule correlates

Select one of the following:

  • self induction, mutual induction and direction of force on a conductor

  • magnetic field, electric field and direction of force on a conductor

  • current, induced emf and direction of force on a conductor

  • current, magnetic field and direction of force on a conductor

Explanation

Question 10 of 36

1

In the left hand rule, thumb always represents

Select one of the following:

  • voltage

  • current

  • direction of force on conductor

  • magnetic field

Explanation

Question 11 of 36

1

The coefficient of coupling between two air core coils depends upon

Select one of the following:

  • self inductance of the two coils only

  • mutual inductance between the two coils onjly

  • mutual inductance and self inductance of the two coils

  • none of the above

Explanation

Question 12 of 36

1

While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electric circuit?

Select one of the following:

  • e.m.f.

  • current density

  • conductivity

  • current

Explanation

Question 13 of 36

1

While comparing magnetic and electric circuits, the point of dissimilarity exists while considering

Select one of the following:

  • flux and current flow

  • permeance and conductance

  • m.m.f. and e.m.f.

  • reluctance and resistance

Explanation

Question 14 of 36

1

The effect of the inductance of a coil on a constant direct current is that

Select one of the following:

  • it strengthens the current

  • it does not affect the constant direct current

  • it decreases the current

  • it causes a higher voltage drop

Explanation

Question 15 of 36

1

Good smoothing factor of a coil depends on the

Select one of the following:

  • terminal voltage

  • property of the wire of the coil

  • inductance of the coil

  • cross-sectional area of the wire of the coil

Explanation

Question 16 of 36

1

Leakage factor is

Select one of the following:

  • less than unity

  • equal to unity

  • more than unity

  • zero

Explanation

Question 17 of 36

1

The law that induces emf and current always opposes the cause producing them was discovered by

Select one of the following:

  • Lenz

  • Faraday

  • Maxwell

  • Ohm

Explanation

Question 18 of 36

1

According to Lenz's law the direction of induced e.m.f. and hence current

Select one of the following:

  • may be found by the right hand rule

  • always opposes the cause producing it

  • is determined by the rate of cutting flux

  • may be found by the left hand rule

Explanation

Question 19 of 36

1

Sparking occurs when a load is switched off because the resistance has high

Select one of the following:

  • capacitance

  • inductance

  • resistance

  • impedance

Explanation

Question 20 of 36

1

The flux linked with a coil of inductance L carrying current i is d/dt(Li)

Select one of the following:

  • True

  • False

  • Partly true

  • Partly false

Explanation

Question 21 of 36

1

When steel toroidal ring is magnetized by passing current through its coil, it develops no magnetic poles

Select one of the following:

  • True

  • False

  • Partly true

  • Partly false

Explanation

Question 22 of 36

1

Air gap in the iron core of an inductor prevents

Select one of the following:

  • hyteresis loss

  • flux change

  • transformer action

  • core saturation

Explanation

Question 23 of 36

1

The growth of current in an inductive circuit follows

Select one of the following:

  • hyperbolic law

  • Ohm's law

  • exponential law

  • linear law

Explanation

Question 24 of 36

1

The time constant of an inductive circuit is defined as

Select one of the following:

  • R/L

  • Rt/L

  • Lt/R

  • L/R

Explanation

Question 25 of 36

1

The time constant is the time it takes the current of an inductive circuit to rise to

Select one of the following:

  • 66% of its final steady state value

  • 70% of its final steady state value

  • 63% of its final steady state value

  • 50% of its final steady state value

Explanation

Question 26 of 36

1

Mutual inductance can also be defined as

Select one of the following:

  • M = N2 dΦ/dt

  • M = N2 dt/di

  • M = N2 di/dt

  • M = N2 dt/dΦ

Explanation

Question 27 of 36

1

The mutual inductance of two coils is maximum when the coils are

Select one of the following:

  • inclined at an angle of 45 degrees

  • at right angle to each other

  • facing each other

  • touching each other

Explanation

Question 28 of 36

1

The value of mutual inductance in terms of self inductance of the two coils L1 and L2 is proportional to

Select one of the following:

  • L1L2

  • L1/L2

  • √L1√L2

  • √L1L2

Explanation

Question 29 of 36

1

Coupling coefficient k, a term much used in radio work can be obtained from

Select one of the following:

  • K = M√L1L2

  • K = M√L1/L2

  • K = M/√L1L2

  • K = ML1L2

Explanation

Question 30 of 36

1

The coupling coefficient denotes

Select one of the following:

  • the degree of magnetic linkage

  • whether the reluctance remains constant

  • the variation of inductance between the two coils

  • whether the flux linkage is constant

Explanation

Question 31 of 36

1

it is difficult to magnetize steel because of its

Select one of the following:

  • low permeability

  • high retentivity

  • high permeability

  • high density

Explanation

Question 32 of 36

1

In electrical machines, laminated cores are used with a view of reducing

Select one of the following:

  • eddy current loss

  • copper loss

  • hysteresis loss

  • windage loss

Explanation

Question 33 of 36

1

The area of hysteresis loop represents hysteresis loss in

Select one of the following:

  • J/m3/s

  • J/cycle

  • J/s

  • J/m3

Explanation

Question 34 of 36

1

According to hysteresis law, hysteresis loss in a material is proportional to

Select one of the following:

  • B^1.2

  • B^1.6

  • B^0.6

  • B^3.6

Explanation

Question 35 of 36

1

A degaussing is the process of

Select one of the following:

  • removing gases from materials

  • removal of magnetic impurities

  • demagnetizing metallic part

  • magnetizing nonmetallic part

Explanation

Question 36 of 36

1

Hysteresis losses can be reduced by

Select one of the following:

  • using grain-oriented silicon steel

  • increasing the frequency of the field

  • laminating the core

  • none of these

Explanation

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