Magnetism - Electricity - Physics Previous Year Questions

1

2016 · Physics · Electricity · Magnetism

WB JEE 2016

An electron enters an electric field having intensity \(E = 3\widehat i + 6\widehat j + 2\widehat k\) Vm^\(-\)1 and magnetic field having induction \(B = 2\widehat i + 3\widehat j\) T with a velocity \(v = 2\widehat i + 3\widehat j\) ms^\(-\)1. The magnitude of the force acting on the electron is (Given, \(e = - 1.6 \times {10^{ - 19}}\) C)

A

1.12 \(\times\) 10^\(-\)18 N

B

5.16 \(\times\) 10^\(-\)16 N

C

3.72 \(\times\) 10^\(-\)17 N

D

4.41 \(\times\) 10^\(-\)18 N

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2

2016 · Physics · Electricity · Magnetism

WB JEE 2016

A rectangular coil carrying-current is placed in a non-uniform magnetic field. On that coil, the total

A

force is non-zero

B

force is zero

C

torque is zero

D

torque is non-zero

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3

2017 · Physics · Electricity · Magnetism

WB JEE 2017

If \(\chi\) stands for the magnetic susceptibility of a substance, \(\mu\) for its magnetic permeability and \(\mu\)₀ for the permeability of free space, then

A

for a paramagnetic substance : \(\chi\) < 0, \(\mu\) > 0

B

for a paramagnetic substance : \(\chi\) > 0, \(\mu\) > \(\mu\)₀

C

for a diamagnetic substance : \(\chi\) > 0, \(\mu\) < 0

D

for a ferromagnetic substance : \(\chi\) > 1, \(\mu\) > \(\mu\)₀

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4

2017 · Physics · Electricity · Magnetism

WB JEE 2017

The magnetic field due to a current in a straight wire segment of length L at a point on its perpendicular bisector at a distance r(r >> L)

A

decreases as \({1 \over r}\)

B

decreases as \({1 \over {{r^2}}}\)

C

decreases as \({1 \over {{r^3}}}\)

D

approaches a finite limit as r \(\to\) \(\infty\)

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5

2017 · Physics · Electricity · Magnetism

WB JEE 2017

A particle with charge e and mass m, moving along the X-axis with a uniform speed u, enters a region where a uniform electric field E is acting along the Y-axis. The particle starts to move in a parabola. Its focal length (neglecting any effect of gravity) is

A

\({{{2m{u^2}} \over {eE}}}\)

B

\({{{eE} \over {2m{u^2}}}}\)

C

\({{{mu} \over {2eE}}}\)

D

\({{{m{u^2}} \over {2eE}}}\)

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6

2017 · Physics · Electricity · Magnetism

WB JEE 2017

The magnets of two suspended coil galvanometers are of the same strength so that they produce identical uniform magnetic fields in the region of the coils. The coil of the first one is in the shape of a square of side a and that of the second one is circular of radius \({a \over {\sqrt \pi }}\). When the same current is passed through the coils, the ratio of the torque experienced by the first coil to that experienced by the second one is

A

1 : \({1 \over {\sqrt \pi }}\)

B

1 : 1

C

\(\pi\) : 1

D

1 : \(\pi\)

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7

2017 · Physics · Electricity · Magnetism

WB JEE 2017

A proton is moving with a uniform velocity of \({{{10}^6}}\) ms^\(-\)1 along the Y-axis, under the joint action of a magnetic field along Z-axis and an electric field of magnitude 2 \(\times\) 10⁴ Vm^\(-\)1 along the negative X-axis. If the electric field is switched off, the proton starts moving in a circle. The radius of the circle is nearly (given : \({e \over m}\) ratio for proton \(\approx\) 10⁸ Ckg^\(-\)1)

A

0.5 m

B

0.2 m

C

0.1 m

D

0.05 m

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8

2017 · Physics · Electricity · Magnetism

WB JEE 2017

Two long parallel wires separated by 0.1 m carry currents of 1A and 2A, respectively in opposite directions. A third current-carrying wire parallel to both of them is placed in the same plane such that it feels no net magnetic force. It is placed at a distance of

A

0.5 m from the 1st wire, towards the 2nd wire

B

0.2 m from the 1st wire, towards the 2nd wire.

C

0.1 m from the 1st wire, away from the 2nd wire

D

0.2 m from the 1st wire, away from the 2nd wire.

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9

2018 · Physics · Electricity · Magnetism

WB JEE 2018

A uniform current is flowing along the length of an infinite, straight, thin, hollow cylinder of radius R. The magnetic field B produced at a perpendicular distance d from the axis of the cylinder is plotted in a graph. Which of the following figures looks like the plot?

A

B

C

D

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10

2018 · Physics · Electricity · Magnetism

WB JEE 2018

A light charged particle is revolving in a circle of radius r in electrostatic attraction of a static heavy particle with opposite charge. How does the magnetic field B at the centre of the circle due to the moving charge depend on r?

A

\(B \propto {1 \over r}\)

B

\(B \propto {1 \over {{r^2}}}\)

C

\(B \propto {1 \over {{r^{3/2}}}}\)

D

\(B \propto {1 \over {{r^{5/2}}}}\)

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11

2018 · Physics · Electricity · Magnetism

WB JEE 2018

A circular loop of radius r of conducting wire connected with a voltage source of zero internal resistance produces a magnetic field B at its centre. If instead, a circular loop of radius 2r, made of same material, having the same cross-section is connected to the same voltage source, what will be the magnetic field at its centre?

A

\({B \over 2}\)

B

\({B \over 4}\)

C

2B

D

B

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12

2018 · Physics · Electricity · Magnetism

WB JEE 2018

A proton of mass m moving with a speed v (< < c, velocity of light in vacuum) completes a circular orbit in time T in a uniform magnetic field. If the speed of the proton is increased to \(\sqrt 2\) v, what will be time needed to complete the circular orbit?

A

\(\sqrt 2\)T

B

T

C

\({{T \over {\sqrt 2 }}}\)

D

\({{T \over 2}}\)

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13

2019 · Physics · Electricity · Magnetism

WB JEE 2019

To which of the following quantities, the radius of the circular path of a charged particle moving at right angles to a uniform magnetic field is directly proportional?

A

energy of the particle

B

magnetic field

C

charge of the particle

D

momentum of the particle

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14

2019 · Physics · Electricity · Magnetism

WB JEE 2019

A square conducting loop is placed near an infinitely long current carrying wire with one edge parallel to the wire as shown in the figure. If the current in the straight wire is suddenly halved, which of the following statements will be true?


"The loop will .........".

A

stay stationary

B

move towards the wire

C

move away from the wire

D

move parallel to the wire

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15

2019 · Physics · Electricity · Magnetism

WB JEE 2019

A particle with charge q moves with a velocity v in a direction perpendicular to the directions of uniform electric and magnetic fields, E and B respectively, which are mutually perpendicular to each other. Which one of the following gives the condition for which the particle moves undeflected in its original trajectory?

A

\(v = {E \over B}\)

B

\(v = {B \over E}\)

C

\(v = \sqrt {{E \over B}}\)

D

\(v = q{B \over E}\)

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16

2019 · Physics · Electricity · Magnetism

WB JEE 2019

A current 'I' is flowing along an infinite, straight wire, in the positive Z-direction and the same current is flowing along a similar parallel wire 5 m apart, in the negative Z-direction. A point P is at a perpendicular distance 3m from the first wire and 4m from the second. What will be magnitude of the magnetic field B of P?

A

\({5 \over {12}}({\mu _0}I)\)

B

\({7 \over {24}}({\mu _0}I)\)

C

\({5 \over {24}}{{{\mu _0}I} \over \pi }\)

D

\({{25} \over {288}}({\mu _0}I)\)

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17

2019 · Physics · Electricity · Magnetism

WB JEE 2019

An electric current 'I' enters and leaves a uniform circular wire of radius r through diametrically opposite points. A particle carrying a charge q moves along the axis of the circular wire with speed v. What is the magnetic force experienced by the particle when it passes through the centre of the circle?

A

\(qv{{{\mu _0}i} \over a}\)

B

\(qv{{{\mu _0}i} \over {2a}}\)

C

\(qv{{{\mu _0}i} \over {2\pi a}}\)

D

Zero

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18

2019 · Physics · Electricity · Magnetism

WB JEE 2019

A metallic loop is placed in a uniform magnetic field B with the plane of the loop perpendicular to B. Under which condition(s) given an emf will be induced in the loop? "If the loop is ............"

A

moved along the direction of B.

B

squeezed to a smaller area

C

rotated about its axis

D

rotated about one of its diameters

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19

2020 · Physics · Electricity · Magnetism

WB JEE 2020

As shown in the figure, a single conducting wire is bent to form a loop in the form of a circle of radius r concentrically inside a square of side a, where a : r = 8 : \(\pi\). A battery B drives a current through the wire. If the battery B and the gap G are of negligible sizes, determine the strength of magnetic field at the common centre O.

A

\({{{\mu _0}I} \over {2\pi a}}\sqrt 2 (\sqrt 2 - 1)\)

B

\({{{\mu _0}I} \over {2\pi a}} (\sqrt 2 + 1)\)

C

\({{{\mu _0}I} \over {\pi a}}2\sqrt 2 (\sqrt 2 + 1)\)

D

\({{{\mu _0}I} \over {\pi a}}2\sqrt 2 (\sqrt 2\) - \(1)\)

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20

2020 · Physics · Electricity · Magnetism

WB JEE 2020

A charged particle moves with constant velocity in a region, where no effect of gravity is felt but an electrostatic field E together with a magnetic field B may be present. Then, which of the following cases are possible?

A

E \(\ne\) 0, B \(\ne\) 0

B

E \(\ne\) 0, B = 0

C

E = 0, B = 0

D

E = 0, B \(\ne\) 0

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