Frage 1
Frage
The coefficient of self-inductance of a coil is defined as
Frage 2
Frage
Which of the following statement is incorrect?
Antworten
-
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.
Frage 3
Frage
Which of the following statements about inductance of a coil is true?
Antworten
-
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.
Frage 4
Frage
A collapsing field around a coil
Antworten
-
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
Frage 5
Frage
Energy stores in an inductance is given by
Antworten
-
2LI2 joules
-
0 joule
-
NΦ/I joules
-
1/2 LI2 joules
Frage 6
Frage
Which of the following is a vector quantity?
Antworten
-
magnetic potential
-
flux density
-
magnetic field intensity
-
relative permeability
Frage 7
Frage
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
Frage 8
Frage
Whenever a conductor cuts magnetic flux, an emf is induced in that conductor. This statement is due to
Antworten
-
Joule's law
-
Coulomb's law
-
Faraday's law
-
Weber and Ewing's theory
Frage 9
Frage
The left hand rule correlates
Antworten
-
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
Frage 10
Frage
In the left hand rule, thumb always represents
Frage 11
Frage
The coefficient of coupling between two air core coils depends upon
Antworten
-
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
Frage 12
Frage
While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electric circuit?
Antworten
-
e.m.f.
-
current density
-
conductivity
-
current
Frage 13
Frage
While comparing magnetic and electric circuits, the point of dissimilarity exists while considering
Frage 14
Frage
The effect of the inductance of a coil on a constant direct current is that
Antworten
-
it strengthens the current
-
it does not affect the constant direct current
-
it decreases the current
-
it causes a higher voltage drop
Frage 15
Frage
Good smoothing factor of a coil depends on the
Frage 16
Antworten
-
less than unity
-
equal to unity
-
more than unity
-
zero
Frage 17
Frage
The law that induces emf and current always opposes the cause producing them was discovered by
Frage 18
Frage
According to Lenz's law the direction of induced e.m.f. and hence current
Antworten
-
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
Frage 19
Frage
Sparking occurs when a load is switched off because the resistance has high
Antworten
-
capacitance
-
inductance
-
resistance
-
impedance
Frage 20
Frage
The flux linked with a coil of inductance L carrying current i is d/dt(Li)
Antworten
-
True
-
False
-
Partly true
-
Partly false
Frage 21
Frage
When steel toroidal ring is magnetized by passing current through its coil, it develops no magnetic poles
Antworten
-
True
-
False
-
Partly true
-
Partly false
Frage 22
Frage
Air gap in the iron core of an inductor prevents
Antworten
-
hyteresis loss
-
flux change
-
transformer action
-
core saturation
Frage 23
Frage
The growth of current in an inductive circuit follows
Antworten
-
hyperbolic law
-
Ohm's law
-
exponential law
-
linear law
Frage 24
Frage
The time constant of an inductive circuit is defined as
Frage 25
Frage
The time constant is the time it takes the current of an inductive circuit to rise to
Antworten
-
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
Frage 26
Frage
Mutual inductance can also be defined as
Antworten
-
M = N2 dΦ/dt
-
M = N2 dt/di
-
M = N2 di/dt
-
M = N2 dt/dΦ
Frage 27
Frage
The mutual inductance of two coils is maximum when the coils are
Frage 28
Frage
The value of mutual inductance in terms of self inductance of the two coils L1 and L2 is proportional to
Frage 29
Frage
Coupling coefficient k, a term much used in radio work can be obtained from
Antworten
-
K = M√L1L2
-
K = M√L1/L2
-
K = M/√L1L2
-
K = ML1L2
Frage 30
Frage
The coupling coefficient denotes
Antworten
-
the degree of magnetic linkage
-
whether the reluctance remains constant
-
the variation of inductance between the two coils
-
whether the flux linkage is constant
Frage 31
Frage
it is difficult to magnetize steel because of its
Antworten
-
low permeability
-
high retentivity
-
high permeability
-
high density
Frage 32
Frage
In electrical machines, laminated cores are used with a view of reducing
Antworten
-
eddy current loss
-
copper loss
-
hysteresis loss
-
windage loss
Frage 33
Frage
The area of hysteresis loop represents hysteresis loss in
Frage 34
Frage
According to hysteresis law, hysteresis loss in a material is proportional to
Frage 35
Frage
A degaussing is the process of
Antworten
-
removing gases from materials
-
removal of magnetic impurities
-
demagnetizing metallic part
-
magnetizing nonmetallic part
Frage 36
Frage
Hysteresis losses can be reduced by