Q.1
A short-circuited coil is placed in time-varying magnetic field. Electrical power is dissipated due to the current induced in the coil. If the number of turns were to be quadrupled and the wire radius halved, the electrical power dissipated would be [ IIT 2002]
  • a) halved
  • b) the same
  • c) doubled
  • d) quadrupled
Q.2
When an AC source of emf e = Eosin(100t) is connected across a circuit, te phase difference between the emf e and the current i in the circuit is observed to be π/4, as shown in the diagram. If the circuit consists possibly only of R-C or R-L or L-C in series, find the relationship between the two elements [ IIT 2003]
ch-18_que_no-230_img_no1.png
  • a) R = 1 kΩ, C = 10µF
  • b) R = 1 kΩ, C = 1µF
  • c) R = 1 kΩ, H = 10 H
  • d) R = 1 kΩ, H = 1 H
Q.3
A small bar magnet is being slowly inserted with constant velocity inside a solenoid as shown in figure. Which graph best represents the relationship between emf and induced with time [ IIT 2004]
ch-18_que_no-231_img_no1.png
  • a)
    ch-18_qn-231choice_img_no1.png
  • b)
    ch-18_qn-231choice_img_no2.png
  • c)
    ch-18_qn-231choice_img_no3.png
  • d)
    ch-18_qn-231choice_img_no4.png
Q.4
An infinitely long cylinder is kept parallel to an uniform magnetic field B directed along positive Z-axis. the direction of induced current as seen from the z-axis will be [ IIT 2005]
  • a) zero
  • b) anticlock wise of +Ve z-axis
  • c) clock wise of the +ve z axis
  • d) along the magnetic field
Q.5
Find the time constant (in µs( from the given RC circuit in the given order respectively. R1 = 1Ω, R2=2Ω, C1 = 4µF, C2 = 2µF [ IIT 2006]
ch-18_que_no-233_img_no1.png
ch-18_que_no-233_img_no2.png
  • a) 18, 4, 8/9
  • b) 18, 8/9, 4
  • c) 4, 18, 8/9
  • d) 4, 8/9, 18
Q.6
The figure shows certain wire segments joined together to form a coplanar loop. The loop is placed in a perpendicular magnetic field in the direction going into the plane of the figure. The magnitude of the field increases with time. I1 and I2 are the currents in the segments ab and cd. Then [ IIT 2009]
ch-18_que_no-234_img_no1.png
  • a) I1 > I2
  • b) I1 < I2
  • c) I1 is in the direction ba and I2 is in the direction cd
  • d) I1 is in the direction ab and I2 is in the direction dc
Q.7
The power factor of an AC circuit having resistance (R) and inductance (L) connected in series and an angular velocity ω is [ AIEEE 2002]
  • a) R/ ωL
  • b) R / (R2 + ω2L2)1/2
  • c) ωL/R
  • d) R / (R2 - ω2L2)1/2
Q.8
A conducting square loop of side L and resistance R moves in its plane with uniform velocity V perpendicular to one of its sides. A magnetic induction B constant in time and space, pointing perpendicular and into the plane at the loop exists everywhere with half the loop outside the field, as shown in figure. The induced emf is { AIEEE 2002]
ch-18_que_no-236_img_no1.png
  • a) zero
  • b) RvB
  • c) VBL/R
  • d) VBL
Q.9
In a transformer, number of turns in primary coil are 140 and that in secondary are If the current in primary coil is 4A, then that in the secondary coil is [ AIEEE 2002]
  • a) 4A
  • b) 2A
  • c) 6A
  • d) 10A
Q.10
Two coils are placed close to each other. the mutual inductance of the pair of coil depends on [ AIEEE 2003]
  • a) the rates at which currents are changing un the two coils
  • b) relative position and orientation of the two coils
  • c) the materials of the wires of the coils
  • d) the currents in the coils
Q.11
When the current changes from +2A to -2A in 0.05 second, an emf of 8V is induced in a coil. the coefficient of self-induction of the coil is [ AIEEE 2003]
  • a) 0.2 H
  • b) 0.4 H
  • c) 0.8 H
  • d) 0.1 H
Q.12
In an oscillating LC circuit the maximum charge on the capacitor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic field is [ AIEEE 2003]
  • a) Q/2
  • b) Q/√3
  • c) Q/√2
  • d) Q
Q.13
The core of any transformer is laminated so as to [ AIEEE 2003]
  • a) reduce the energy loss due to eddy currents
  • b) make it light weight
  • c) make it robust and strong
  • d) increases the secondary voltage
Q.14
Alternating current can not be measured by D.C. ammeter because [ AIEEE 2004]
  • a) average value of current for complete cycle is zero
  • b) A.C. changes direction
  • c) A.C. can not pass through D.C. Ammeter
  • d) D.C. Ammeter will get damaged
Q.15
In an LCR series a.c. circuit, the voltage across each of the components L, C and R is 50V. The voltage across the LC combination will be [ AIEEE 2004]
  • a) 100V
  • b) 50√2 V
  • c) 50 V
  • d) zero
Q.16
A coil having n turns and resistance RΩ is connected with a galvanometer of resistance 4RΩ This combination is moved in time t seconds from a magnetic field W1 weber to W2 weber. The induced current in the circuit is [ AIEEE 2004]
  • a)
    ch-18_qn-244choice_img_no1.png
  • b)
    ch-18_qn-244choice_img_no2.png
  • c)
    ch-18_qn-244choice_img_no3.png
  • d)
    ch-18_qn-244choice_img_no4.png
Q.17
In a uniform magnetic field of induction B a wire in the form of semicircle of radius r rotates about the diameter of the circle with an angular frequency ω. The axis of rotation is perpendicular to the field. If the total resistance of the circuit is R, the mean power generated per period of rotation is [ AIEEE 2004]
  • a) (Bπrω)2 / 2R
  • c) (Bπr2ω) / 2R
  • d) (Bπrω2)2 / 8R
  • b) (Bπr2ω)² / 8R
Q.18
In a LCR circuit capacitance is changed from C to 2C. For the resonant frequency to remain unchanged, the inductance should be changed from L to [ AIEEE 2004]
  • a) L/2
  • b) 2L
  • c) 4L
  • d) L/4
Q.19
one conducting U tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field B is perpendicular to the plane of the figure. If each tube moves towards the other at a constant speed v, then the emf induced in the circuit in terms of B, l and V where l is the width of each tube will be [ AIEEE 2005]
ch-18_que_no-247_img_no1.png
  • a) - Blv
  • b) Blv
  • c) 2Blv
  • d) zero
Q.20
The self inductance of the motor of an electric fan is 10H. In order to impart maximum power at 50Hz, it should be connected to a capacitance of [ AIEEE 2005]
  • a) 8µF
  • b) 4µD
  • c) 2µF
  • d) 1µF
Q.21
The phase difference between the alternating current and emf is π/Which of the following cannot be the constituent of circuit [ AIEEE 2005]
  • a) R,L
  • b) C alone
  • c) L alone
  • d) L, C
Q.22
A circuit has a resistance of 12Ω and an impedance of 15Ω. The power factor of the circuit will be [ AIEEE 2005]
  • a) 0.4
  • b) 0.8
  • c) 0.125
  • d) 1.25
Q.23
A coil of inductance 300mH and resistance 2Ω is connected to a source of voltage 2V. The current reaches half of its steady state value in [ AIEEE 2005]
  • a) 0.1 s
  • b) 0.05s
  • c) 0.3s
  • d) 0.15s
Q.24
Which of the following units denote the dimension ML2 / QWhere Q denotes electric charge? [ AIEEE 2006]
  • a) Wb/m²
  • b) Henry (H)
  • d) Weber(Wb)
  • c) H/m²
Q.25
The flux linked with coil at any instant 't' is given by φ = 10t2 - 50t +250 The induced emf at t = 3s is [ AIEEE 2006]
  • a) -190 V
  • b) -10 V
  • c) 10 V
  • d) 190 V
Q.26
An inductor (L = 100 mH) a resistor ( R = 100Ω) and a battery (E = 100 V) are initially connected in series as shown in figure. After a long time the battery is disconnected after short circuiting the point A and B. the current in the circuit 1 ms after the short circuit is [ AIEEE 2006]
ch-18_que_no-255_img_no1.png
  • a) 1/e A
  • b) e A
  • c) 0.1 A
  • d) 1 A
Q.27
In an a.c. circuit the voltage applied is E = Eosinωt. the resulting current in the circuit is I = Iosin( ωt - π/2). The power consumption in the circuit is given by [ AIEEE 2007]
  • a) P = √2 EoIo
  • b) P = (EoIo) / √2
  • c) P = zero
  • d) P = EoIo / 2
Q.28
An ideal coil of 10H is connected in series with a resistance of 5Ω and a battery of 5V. 2 second after the connection is made, the current flowing in ammeter in the circuit is [ AIEEE 2007]
  • a) (1 - e-1)
  • b) (1 - e)
  • c) e
  • d) e-1
Q.29
two coaxial solenoids are made by winding thin insulated wire over a pipe of cross-sectional area A = 10 cm2 and length = 20 cm. If one of the solenoid has 300 turns and other 400 turns, their mutual inductance is [ AIEEE 2008]
  • a) 2.4π ×10-5 H
  • b) 4.8π ×10-4 H
  • c) 4.8π ×10-5 H
  • d) 2.4π ×10-4 H
Q.30
An inductor of inductance L = 400 mH and resistor of resistance R1 = 2Ω are connected to a battery of emf 12V as shown in figure. The internal resistance of the battery is negligible. The switch S is closed at t=The potential drop across L as a function of time is [ AIEEE 2009]
ch-18_que_no-259_img_no1.png
  • a)
    ch-18_qn-259choice_img_no1.png
  • b)
    ch-18_qn-259choice_img_no2.png
  • c)
    ch-18_qn-259choice_img_no3.png
  • d)
    ch-18_qn-259choice_img_no4.png
0 h : 0 m : 1 s