Multiple Choice QuestionsWhen sound waves travel from air to water which one of the following remains constant?
Time period
Frequency
Velocity
Wavelength
A choke is preferred to a resistance for limiting current in AC circuit because
choke is cheap
there is no wastage of power
choke is compact in size
choke is a good absorber of heat
B.
there is no wastage of power
In an AC circuit, the coil of high inductance and negligible resistance used to control current, is called the choke coil. The power factor of such a coil is given by
cos =
≈ ...( as R<< ωL )
As R << ωL, cos is very small.
Thus, the power absorbed by the coil is very small. The only loss of energy is due to hysteresis in the iron core, which is much less than the loss of energy in the resistance that can also reduce the current if placed instead of the choke coil.
A current of 5A is passing through a metalic wire of cross-sectional area 4 × 10-6 m2 . If the density of charge carriers of the wire is 5 × 1026 m-3, then the drift velocity of the electrons will be
1 × 102 m/s
1.56 × 10-2 m /s
1.56 × 10-3 m/s
1 × 10-2 m/s
A galvanometer can be changed into an ammeter by using
low resistance shunt in series
low resistance shunt in parallel
high resistance shunt in series
high resistance shunt in parallel
A proton moving vertically downward enters a magnetic field pointing towards north. In which direction proton will deflect?
East
West
North
South
Induced emf in the coil depends upon
conductivity of coil
amount of flux
rate of change of linked flux
resistance of coil
X-rays are used in determining the molecular structure of crystalline because
its energy is high
it can penetrate the material
its wavelength is comparable to interatomic distance
its frequency is low
Kirchhoff's law of junction, ΣI = 0, is based on
conservation of energy
conservation of charge
conservation of energy as well as charge
conservation of momentum
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