Q.1
One 10V, 60 W bulb is to be connected to 100V line. The required induction coil has self-induction of value ( f = 50HZ) [ RajPET 1997]
  • a) 0.052 H
  • b) 2.42 H
  • c) 16.2 mH
  • d) 1.62 mH
Q.2
A 120 volt A.C. source is connected across a pure inductor of inductance 0.70 henry. If the frequency of the source is 60Hz, the current passing through the inductor is [ MPPMT 1994]
  • a) 4.55 amp
  • b) 0.355 amp
  • c) 0.455 amps
  • d) 3.55 amps
Q.3
The wattless circuit is obtained when phase difference between virtual voltage and virtual current is [ Raj.PET 1996]
  • a) 90°
  • b) 45°
  • c) 180°
  • d) 60°
Q.4
The coefficient of inductance of a choke coil is 0.1H and resistance is 12Ω. If it is connected to an alternating current source of frequency 60Hz, then power factor will be [ Raj.PET 1997]
  • a) 0.32
  • b) 0.30
  • c) 0.28
  • d) 0.24
Q.5
The peak value of A.C. current is 2√2, its virtual value will be [ Raj.PMT 1996]
  • a) 1A
  • b) 2A
  • c) 4A
  • d) zero
Q.6
In A.C circuit the emf and current are given by E = 200 sin314t volt and I = sin(314t + π/3). The power factor will be [ Raj.PMT 1996]
  • a) 1/2
  • b) 1/4
  • c) 1
  • d) -1
Q.7
The coefficient of induction of choke coil is 0.1 H and resistance is 12Ω. If it is connected to an alternating current source of frequency 60Hz, then power factor will be [ Raj.PET 1997]
  • a) 0.32
  • b) 0.30
  • c) 0.28
  • d) 0.24
Q.8
When the key K is pressed at time t = 0, which of the following statements about the current I in the resistor AB of the given circuit is true? [ CBSE 1995]
ch-18_que_no-218_img_no1.png
  • a) I = 2mA at all t
  • b) I oscillates between 1mA and 2mA
  • c) I = 1mA at all t
  • d) At t = 0, I = 2mA and with time it goes to 1mA
Q.9
An alternating current source of frequency 100Hz is joined to a combination of resistance, a capacitance and a coil in series. The potential difference across the coil, the resistance and the capacitor is 46, 8 and 40Volt respectively. The electromotive force of alternating current source in volt is [ MPPMT 1995]
  • a) 94
  • b) 14
  • c) 10
  • d) 76
Q.10
Q220) A thin circular ring of area A is held perpendicular to a uniform magnetic field of induction B. A small cut is made in the ring and a galvanometer is connected across the ends such that the total resistance of the circuit is R. When the ring is suddenly squeezed to zero area, the charge flowing through galvanometer is [ 1995]
  • a) BR/A
  • b) AB/R
  • c) ABR
  • d) B2A / R2
Q.11
A thin semicircular conducting ring of radius R is falling with its plane vertical in horizontal magnetic field induction B. At the position MNQ the speed of the ring is c, and the potential difference developed across the ring is [ IIT 1996]
ch-18_que_no-221_img_no1.png
  • a) zero
  • b) BvπR2 / 2 and M is at higher potential
  • c) πRBv and Q is at higher potential
  • d) 2RBv and Q is at higher potential
Q.12
Two identical circular loops of metal wire are lying on a table without touching each other. Loop A carries a current which increases with time. In response, the loop-B [ IIT 1999]
  • a) remains stationary
  • b) is attracted by loop A
  • c) is repelled by loop A
  • d) rotates about its Cm, with CM fixed
Q.13
A coil of inductance 8.4mH and resistance 6Ω is connected to a 12V battery. The current in the coil is 1.0A at approximately the time [ IIT 1999]
  • a) 500 s
  • b) 5 s
  • c) 35 ms
  • d) 1 ms
Q.14
A uniform but time-varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of the paper, as shown. The magnitude of the induced electric field at a point P at a distance r from the centre of the circular region [ IIT 2000]
ch-18_que_no-224_img_no1.png
  • a) is zero
  • b) decreases as 1/r
  • c) increases as r
  • d) decreases as 1/r2
Q.15
A coil of wire having inductance and resistance has a conducting ring placed coaxially within it. The coil is connected to a battery at time t= 0, so that a time dependent current I1(t) starts flowing through the coil. If I2(t) is the current induced in the ring, and B(t) is the magnetic field at the axis of the coil due to I1(t), the product I2B(t)[ IIT 2000]
  • a) increases with time
  • b) decreases with time
  • c) does not vary with time
  • d) passes through a maximum
Q.16
A metallic square loop ABCD is moving in its own plane with velocity v in a uniform magnetic field perpendicular to its plane as shown in figure. An electric field is included [ 2001]
ch-18_que_no-226_img_no1.png
  • a) in AD, but not in BC
  • b) in BC, but not in AD
  • c) neither in AD nor in BC
  • d) in both AD and BC
Q.17
Two circular coils can be arranged in any of the three situations shown in the figure. Their mutual inductance will be [ IIT 2001]
ch-18_que_no-227_img_no1.png
  • a) maximum in situation(a)
  • b) maximum in situation (b)
  • c) maximum un situation (c)
  • d) the same in all situations
Q.18
As shown in the figure, P and Q are two coaxial conducting loops separated by some distance. When the switch S is closed, a clockwise current Ip flows in P( as seen by E) and an induced current IQ1 flows in Q. The switch remains closed for a long time. When S is opened, a current IQ2 flows in Q. Then the direction IQ1 and IQ2 ( as seen by E) are [ IIT 2002]
ch-18_que_no-228_img_no1.png
  • a) respectively clockwise and anti-clockwise
  • b) both clockwise
  • c) both anti-clockwise
  • d) respectively anti-clockwise and clockwise
Q.19
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.20
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.21
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.22
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.23
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.24
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.25
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.26
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.27
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.28
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.29
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.30
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
0 h : 0 m : 1 s