A transformer is employed to
A)
Convert A.C. into D.C.
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B)
Convert D.C. into A.C.
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C)
Obtain a suitable A.C. voltage
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D)
Obtain a suitable D.C. voltage
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To convert mechanical energy into electrical energy, one can use
A)
DC dynamo
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B)
AC dynamo
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C)
Motor
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D)
[a] & [b]
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The phenomenon of electromagnetic induction is
A)
The process of charging a body.
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B)
The process of generating magnetic field due to a current passing through a coil.
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C)
Producing induced current in a coil due to relative motion between a magnet and the coil.
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D)
The process of rotating a coil of an electric motor.
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At the time of short circuit, the current in the circuit
A)
Reduces substantially
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B)
does not change.
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C)
Increases heavily
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D)
vary continuously
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For dynamo which one of the following statements is correct
A)
It converts the electrical energy into light energy
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B)
It converts the kinetic energy into heat energy
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C)
It converts the mechanical energy into electrical energy
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D)
It converts the electrical energy into mechanical energy
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A conducting wire is dropped along east-west direction, then
A)
No emf is induced
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B)
No induced current flows
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C)
Induced current flows from west to east
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D)
Induced current flows from east to west
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Core of transformer is made up of
A)
Soft iron
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B)
Steel
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C)
Iron
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D)
Alnico
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Fan is based on
A)
Electric Motor
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B)
Electric dynamo
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C)
Both
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D)
None of these
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The core of a transformer is laminated so that
A)
Ratio of voltage in the primary and secondary may be increased
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B)
Rusting of the core may be stopped
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C)
Energy losses due to eddy currents may be reduced
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D)
Change in flux is increased
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Large transformers, when used for some time, become hot and are cooled by circulating oil. The heating of transformer is due to
A)
Heating effect of current alone
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B)
Hysteresis loss alone
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C)
Both the hysteresis loss and heating effect of current
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D)
None of the above
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Alternating current cannot be measured by dc ammeter because
A)
ac cannot pass through dc ammeter
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B)
Average value of complete cycle is zero
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C)
ac is virtual
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D)
ac changes its direction
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A bulb is connected first with DC and then AC of same voltage it will shine brightly with
A)
AC
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B)
DC
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C)
Brightness will be in ratio 1/1.4
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D)
Equally with both
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The voltage of domestic AC is 220 volt. What does this represent
A)
Mean voltage
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B)
Peak voltage
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C)
Root mean voltage
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D)
Root mean square voltage
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Radio frequency choke uses core of
A)
Air
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B)
Iron
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C)
Air and Iron
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D)
None of these
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Quantity that remains unchanged in a transformer is
A)
Voltage
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B)
Current
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C)
Frequency
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D)
None of the above
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For high frequency, a capacitor offers
A)
More reactance
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B)
Less reactance
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C)
Zero reactance
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D)
Infinite reactance
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When the number of turns in a coil is doubled without any change in the length of the coil, its self-inductance becomes
A)
Four times
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B)
Doubled
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C)
Halved
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D)
Unchanged
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When a metallic plate swings between the poles of a magnet
A)
No effect on the plate
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B)
Eddy current are set up inside the plate and the direction of the current is along the motion of the plate
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C)
Eddy currents are set up inside the plate and the direction of the current oppose the motion of the plate
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D)
Eddy currents are set up inside the plate
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A long horizontal metallic rod with length along the east-west direction is falling under gravity. The potential difference between its two ends will be
A)
Zero
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B)
Constant
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C)
Increase with time
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D)
Decrease with time
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What is the function of oil in a transformer?
A)
It provides insulation
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B)
It provides cooling
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C)
It provides smoothness
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D)
Both [a] and [b]
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