A 20V ac is applied to a circuit consisting of a resistance and a coil with negligible resistance. If the voltage across the resistance is 12 V the voltage across the coil is10 V8 V6 V
1.16 V
2.10 V
3.8 V
4.6 V
A bar magnet falls through a metal ring. The acceleration will be
1.equal to g
2.less than g
3.greater than g
4.zero
A step down transformer reduces 200 V to 110 V. The primary draws 5 amp. of current and secondary supplies 9 ampere. The efficiency of transformer is90%80%60%70%
1.90%
2.80%
3.60%
4.70%
A transformer is used to light a 100W and 110 V lamp from a 230 V mains If the main current is 05 A the efficiency of the transformer is
1.50%
2.20%
3.87%
4.67%
An AC voltmeter reads 20 V across a resistor 30 V across an inductor and 15 V across a capacitor in LCR series circuit In this case the supply voltage will be
1.100 V
2.60 V
3.50 V
4.25 V
Eddy currents are also known as
1.Focault currents
2.Faraday currents
3.Huygen currents
4.Franklin currents
Electromagnetic induction is the underlying phenomenon in the construction of
1.galvanometer
2.pyrometer
3.pyrometer
4.generator
If an e. m. f. of 300 micro volts is induced in a coil when current in it changes from 13 amperes to 7 amperes in 0.5 sec then the value of the self inductance of the coil will be25 micro henry20 micro henry27 micro henry
1.25 micro henry
2.20 micro henry
3.27 micro henry
4.17 micro henry
If in a galvanometer the coil is wound on a bad conductor the eddy current will be
1.zero
2.maximum
3.minimum
4.50% of the actual value
L / R has the dimensions ofhenrytime
1.mass
2.length
3.henry
4.time
Lenz s law gives the
1.magnitude of induced e. m. f.
2.magnitude of induced current
3.direction of current/emf induced
4.None of these
Lenzs law is a consequence of the law of conservation ofmassenergy
1.mass
2.energy
3.momentum
4.charge
The alternating voltage which we use in house has a peak value of nearly
1.220 V
2.280 V
3.311 V
4.300 V
The coil of a moving coil galvanometer is wound over metallic frames so that due to eddy currents the motion
1.remains the same
2.is damped
3.undamped
4.is made oscillatory
The frequency of ac in India is
1.50 Hz
2.50 kHz
3.1420 MHz
4.60 kHz
The laws of electromagnetic induction are the contribution of
1.Faraday
2.Maxwell
3.Lawrence
4.Hall
The principle of eddy currents is used in
1.galvanometer
2.speedometer
3.pyrometer
4.barometer
The property of an electric circuit by virtue of which any change in the magnetic flux linked with it induces an e m f in it is called
1.self-inductance
2.conductance
3.mutual induction
4.trans-conductance
The S.I. unit of magnitude flux is
1.Maxwell
2.Tesla
3.Weber
4.Henry
When power is drawn from the secondary coil of the transformer the dynamic resistance
1.remains same
2.decreases
3.increases
4.fluctuates.