Q.1
A transformer connected to 220 volt line shows an out put of 2A at 11000 volt. The efficiency is 100%. The current drawn from the line is [ PMT 1995]
  • a) 100A
  • b) 200A
  • c) 22A
  • d) 11A
Q.2
In a circuit with a coil of resistance 2Ω the magnetic flux changes from 2Wb to 10.0 Wb in 0.2 second. The charge that flows in the coil during this time is [ MPPMT 1997]
  • a) 5.0 coulomb
  • b) 4.0 coulomb
  • c) 1.0 coulomb
  • d) 0.8 coulomb
Q.3
The primary winding of a transformer has 500 turns where as its secondary has 500 turns. The primary is connected to an a.c supply of 20V, 50Hz. The secondary will have an output of [ CBSE 1997]
  • a) 200v, 50Hz
  • b) 20V, 500Hz
  • c) 2V, 50Hz
  • d) 2V, 5Hz
Q.4
Two identical coaxial circular loops carry current I each circulating in the clockwise direction. If the loops are approaching each other, then [ PMT 1995]
  • a) current in each loop increases
  • b) current in each loop remains the same
  • c) current in each loop decreases
  • d) current in one loop increases and in the other it decreases
Q.5
A magnet is brought near a ring a) quickly b) slowly, induced emf will be [ Raj.PMT 1997]
  • a) More in case(a)
  • b) Less in case (a)
  • c) same in both the cases
  • d) Depends on the radius of ring
Q.6
Two loops of different wires are placed concentrically in a plane. If the current in the outer loop is made to pass clockwise and current increases with time, the induced current in the inner loop will be [ Rj.PET 1996]
  • a) clockwise
  • b) anticlockwise
  • c) zero
  • d) will depend upon the radius of loop
Q.7
Mutual inductance of two coils can be increased by [ MPPMT 1994]
  • a) Decreasing the number of turns in the coils
  • b) Increasing the number of turns in the coils
  • c) Winding the coils on wooden core
  • d) None of above
Q.8
The number of turns of primary and secondary coils of a transformer are 5 and 10, respectively and the mutual inductance of the transformer is 25henry. Now the number of turns in the primary and secondary of the transformer are made 10 and 5 respectively. the mutual inductance of the transformer in Henry will be [ MPPET 1995]
  • a) 6.25
  • b) 12.5
  • c) 25
  • d) 50
Q.9
The mutual inductance between a primary and secondary circuit is 0.5H. The resistance of the primary and the secondary circuit are 20Ω and 5Ω respectively. To generate a current of 0.4A in the secondary, the current in the primary must be changed at the rate of [ MPPMT 1997]
  • a) 4.0A/s
  • b) 16.A/s
  • c) 1.6A/s
  • d) 8.0A/s
Q.10
The secondary of transformer gives 200 volts when 2.0 kilowatt power is suppled to its 500 turn primary at 0.5 ampere. The number of turns in the secondary is [ AMU 1995]
  • a) 25
  • b) 30
  • c) 35
  • d) 40
Q.11
Tick out the wrong statement [ AMU 1995]
  • a) An emf can be inducted between the ends of a straight conductor by moving the ends of a straight conductor by moving it through a uniform magnetic field
  • b) The self induced emf produced by changing current in a coil always tends to decrease the current
  • c) Inserting an iron core in a coil increases the coefficient of self-inductance
  • d) According to lenz's law, direction of the induced current is such that it opposes the flux change that causes it
Q.12
The self-inductance of a coil is L. Keeping the length and area same, the number of turns in the coil is increased to four times. the self inductance of the coil will now be [ MPPMT 1997]
  • a) L/4
  • b) L
  • c) 4L
  • d) 16L
Q.13
A galvanometer is connected to the secondary coil. The galvanometer shows an instantaneous deflection of 7 division when current is started in primary coil of solenoid. Now if primary coil is suddenly rotated through 180°, then the new instantaneous deflection will be [ CPMT 1991]
  • a) 7 units
  • b) 14 units
  • c) zero units
  • d) 21 units
Q.14
An emf E = 4cos(1000 t) volt is applied to an LR-circuit of inductance 3mH and resistance 4Ω. The amplitude of current in the circuit is [ MPPMT 1997]
  • a) 4/√7 A
  • b) 1.0A
  • c) 4/7 A
  • d) 0.8 A
Q.15
The average power dissipation in pure inductance is [ MPPET 1999]
  • a) ½ LI2
  • b) 2LI2
  • c) ¼ LI2
  • d) zero
Q.16
A choke coil has [ Raj.PMT 1997]
  • a) high inductance an high resistance
  • b) low inductance and low resistance
  • c) high inductance and low resistance
  • d) low inductance and high resistance
Q.17
In an A.C. circuit, the resonance is obtained when [ Raj/.PET 1996]
  • a) Z = R
  • b) Z = ωL - (1/ ωC)
  • c) L and C are in same phase
  • d) The phase in C varies with source voltage
Q.18
An L.C.R circuit is connected to a source of alternating current. At resonance, the applied voltage and current flowing through the circuit will have a phase difference of [ CBSE 1994]
  • a) π/4
  • b) zero
  • c) π
  • d) π/2
Q.19
In an LR-circuit, the inductive reactance is equal to the resistance R of the circuit. An emf E = Eocosωt is applied to the circuit. The power consumed in the circuit is [ MPPMT 1997]
  • a) Eo2 / R
  • b) Eo2 / 2R
  • c) Eo2 /4R
  • d) Eo2 / 8R
Q.20
The current in resistance R at resonance is [ CPMT 1993]
ch-18_que_no-154_img_no1.png
  • a) zero
  • b) Minimum but finite
  • c) Maximum but finite
  • d) Infinite
Q.21
The resistance of coil at frequency 104 Hz is 104 Ω, the reactance at 2×104 Hz frequency will become [ Raj.PMT 1996]
  • a) 104 Ω
  • b) 2×104 Ω
  • c) 3×107 Ω
  • d) 4×104 Ω
Q.22
In pure resistance A.C. circuit the phase difference between current and voltage is [ Rj.PMT 1996]
  • a) zero
  • b) π/2
  • c) -π/2
  • d) π/4
Q.23
An alternating current of frequency f is flowing in a circuit containing a resistance R and a choke L in series. The impedance of the circuit is equal to [ MPPET 1999]
  • a) R
  • b) R +πfL
  • c) √[ R2 +4π2f2L2]
  • d) R/2πfL
Q.24
A 10Ω resistance, 5mH coil and 10µF capacitor are joined in series. When a suitable frequency alternating current source is joined to this combination, the circuit resonates. If the resistance is halved, the resonance frequency [ MPPET 1995]
  • a) is halved
  • b) is doubled
  • c) remain unchanged
  • d) is quadrupled
Q.25
The frequency for which a 5.0µF capacitor has a reactance of 1000Ω is given by [ MPPMT 1993]
  • a) 1000/π cycles/sec
  • b) 100/π cycles/sec
  • c) 200 cycles/sec
  • d) 5000 cycles/sec
Q.26
In an AC circuit, a resistance of RΩ is connected in series with an inductance L. If phase angle between voltage and current be 45°, the value of inductive reactance will be [ MPPMT 1998]
  • a) R/4
  • b) R/2
  • c) R
  • d) can not found with the given data
Q.27
In an A.C circuit. V and I are given by V = 100sin100t volts and I = 100sin(100t + π/3) mA. The power dissipated in the circuit is [ MPPMT 1999]
  • a) 104 watts
  • b) 10 watts
  • c) 2.5 watts
  • d) 50 watts
Q.28
In a series resonant circuit, the a.c. voltage across resistance R, inductance L and capacitance C are 5V, 10V and 10V respectively. The a.c. voltage applied to the circuit will be [ CET 1994]
  • a) 20 V
  • b) 10 V
  • c) 5 V
  • d) 25 V
Q.29
The impedance of a circuit consists of 3Ω resistance and 4Ω reactance. The power factor of the circuit is [ MPPMT 1994]
  • a) 0.4
  • b) 0.6
  • c) 0.8
  • d) 1.0
Q.30
Same current is flowing in two alternating circuits. The first circuit contains only inductance and the other contains only a capacitor. If the frequency of the emf is increased the effect on the value of the current will be [ MPPMT 1993]
  • a) Increase in first circuit and decrease in the other
  • b) Increase in both circuits
  • c) Decrease in both circuits
  • d) Decrease in first circuit and increase in the other
0 h : 0 m : 1 s