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ELECTROMAGNETIC INDUCTION

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Engineering Quiz on ELECTROMAGNETIC INDUCTION, created by Owen Ryan Ang on 24/01/2020.
Owen Ryan Ang
Quiz by Owen Ryan Ang, updated more than 1 year ago
Owen Ryan Ang
Created by Owen Ryan Ang over 4 years ago
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Resource summary

Question 1

Question
The coefficient of self-inductance of a coil is defined as
Answer
  • NI/Φ
  • NΦ/I
  • Φ/NI
  • ΦI/N

Question 2

Question
Which of the following statement is incorrect?
Answer
  • 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.

Question 3

Question
Which of the following statements about inductance of a coil is true?
Answer
  • 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.

Question 4

Question
A collapsing field around a coil
Answer
  • 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

Question 5

Question
Energy stores in an inductance is given by
Answer
  • 2LI2 joules
  • 0 joule
  • NΦ/I joules
  • 1/2 LI2 joules

Question 6

Question
Which of the following is a vector quantity?
Answer
  • magnetic potential
  • flux density
  • magnetic field intensity
  • relative permeability

Question 7

Question
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
Answer
  • BLI
  • zero
  • B2LI
  • BL2I

Question 8

Question
Whenever a conductor cuts magnetic flux, an emf is induced in that conductor. This statement is due to
Answer
  • Joule's law
  • Coulomb's law
  • Faraday's law
  • Weber and Ewing's theory

Question 9

Question
The left hand rule correlates
Answer
  • 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

Question 10

Question
In the left hand rule, thumb always represents
Answer
  • voltage
  • current
  • direction of force on conductor
  • magnetic field

Question 11

Question
The coefficient of coupling between two air core coils depends upon
Answer
  • 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

Question 12

Question
While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electric circuit?
Answer
  • e.m.f.
  • current density
  • conductivity
  • current

Question 13

Question
While comparing magnetic and electric circuits, the point of dissimilarity exists while considering
Answer
  • flux and current flow
  • permeance and conductance
  • m.m.f. and e.m.f.
  • reluctance and resistance

Question 14

Question
The effect of the inductance of a coil on a constant direct current is that
Answer
  • it strengthens the current
  • it does not affect the constant direct current
  • it decreases the current
  • it causes a higher voltage drop

Question 15

Question
Good smoothing factor of a coil depends on the
Answer
  • terminal voltage
  • property of the wire of the coil
  • inductance of the coil
  • cross-sectional area of the wire of the coil

Question 16

Question
Leakage factor is
Answer
  • less than unity
  • equal to unity
  • more than unity
  • zero

Question 17

Question
The law that induces emf and current always opposes the cause producing them was discovered by
Answer
  • Lenz
  • Faraday
  • Maxwell
  • Ohm

Question 18

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

Question 19

Question
Sparking occurs when a load is switched off because the resistance has high
Answer
  • capacitance
  • inductance
  • resistance
  • impedance

Question 20

Question
The flux linked with a coil of inductance L carrying current i is d/dt(Li)
Answer
  • True
  • False
  • Partly true
  • Partly false

Question 21

Question
When steel toroidal ring is magnetized by passing current through its coil, it develops no magnetic poles
Answer
  • True
  • False
  • Partly true
  • Partly false

Question 22

Question
Air gap in the iron core of an inductor prevents
Answer
  • hyteresis loss
  • flux change
  • transformer action
  • core saturation

Question 23

Question
The growth of current in an inductive circuit follows
Answer
  • hyperbolic law
  • Ohm's law
  • exponential law
  • linear law

Question 24

Question
The time constant of an inductive circuit is defined as
Answer
  • R/L
  • Rt/L
  • Lt/R
  • L/R

Question 25

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

Question 26

Question
Mutual inductance can also be defined as
Answer
  • M = N2 dΦ/dt
  • M = N2 dt/di
  • M = N2 di/dt
  • M = N2 dt/dΦ

Question 27

Question
The mutual inductance of two coils is maximum when the coils are
Answer
  • inclined at an angle of 45 degrees
  • at right angle to each other
  • facing each other
  • touching each other

Question 28

Question
The value of mutual inductance in terms of self inductance of the two coils L1 and L2 is proportional to
Answer
  • L1L2
  • L1/L2
  • √L1√L2
  • √L1L2

Question 29

Question
Coupling coefficient k, a term much used in radio work can be obtained from
Answer
  • K = M√L1L2
  • K = M√L1/L2
  • K = M/√L1L2
  • K = ML1L2

Question 30

Question
The coupling coefficient denotes
Answer
  • the degree of magnetic linkage
  • whether the reluctance remains constant
  • the variation of inductance between the two coils
  • whether the flux linkage is constant

Question 31

Question
it is difficult to magnetize steel because of its
Answer
  • low permeability
  • high retentivity
  • high permeability
  • high density

Question 32

Question
In electrical machines, laminated cores are used with a view of reducing
Answer
  • eddy current loss
  • copper loss
  • hysteresis loss
  • windage loss

Question 33

Question
The area of hysteresis loop represents hysteresis loss in
Answer
  • J/m3/s
  • J/cycle
  • J/s
  • J/m3

Question 34

Question
According to hysteresis law, hysteresis loss in a material is proportional to
Answer
  • B^1.2
  • B^1.6
  • B^0.6
  • B^3.6

Question 35

Question
A degaussing is the process of
Answer
  • removing gases from materials
  • removal of magnetic impurities
  • demagnetizing metallic part
  • magnetizing nonmetallic part

Question 36

Question
Hysteresis losses can be reduced by
Answer
  • using grain-oriented silicon steel
  • increasing the frequency of the field
  • laminating the core
  • none of these
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