Electrostatics - Electricity - Physics Previous Year Questions

1

2016 · Physics · Electricity · Electrostatics

WB JEE 2016

Angle between an equipotential surface and electric lines of force is

A

0\(^\circ\)

B

90\(^\circ\)

C

180\(^\circ\)

D

270\(^\circ\)

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2

2016 · Physics · Electricity · Electrostatics

WB JEE 2016

A hollow metal sphere of radius R is charged with a charge Q. The electric potential and intensity inside the sphere are respectively

A

\({Q \over {4\pi {\varepsilon _0}{R^2}}}\) and \({Q \over {4\pi {\varepsilon _0}R}}\)

B

\({Q \over {4\pi {\varepsilon _0}R}}\) and zero

C

zero and zero

D

\({{4\pi {\varepsilon _0}Q} \over R}\) and \({Q \over {4\pi {\varepsilon _0}{R^2}}}\)

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3

2016 · Physics · Electricity · Electrostatics

WB JEE 2016

A charged particle of mass m₁ and charge q₁ is revolving in a circle of radius r. Another charged particle of charge q₂ and mass m₂ is situated at the centre of the circle. If the velocity and time period of the revolving particle be v and T respectively, then

A

\(v = \sqrt {{{{q_1}{q_2}r} \over {4\pi {\varepsilon _0}{m_1}}}}\)

B

\(v = {1 \over {{m_1}}}\sqrt {{{{q_1}{q_2}} \over {4\pi {\varepsilon _0}r}}}\)

C

\(T = \sqrt {{{16{\pi ^3}{\varepsilon _0}m_1^2{r^3}} \over {{q_1}{q_2}}}}\)

D

\(T = \sqrt {{{16{\pi ^3}{\varepsilon _0}m_1^{}{r^3}} \over {{q_1}{q_2}}}}\)

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4

2017 · Physics · Electricity · Electrostatics

WB JEE 2017

A positive charge Q is situated at the centre of a cube. The electric flux through any face of the cube is (in SI units)

A

\({Q \over {6{\varepsilon _0}}}\)

B

\(4\pi Q\)

C

\({Q \over {4\pi {\varepsilon _0}}}\)

D

\({Q \over {6\pi {\varepsilon _0}}}\)

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5

2017 · Physics · Electricity · Electrostatics

WB JEE 2017

A particle with charge Q coulomb, tied at the end of an inextensible string of length R metre, revolves in a vertical plane. At the centre of the circular trajectory, there is a fixed charge of magnitude Q coulomb. The mass of the moving charge M is such that \(Mg = {{{Q^2}} \over {4\pi {\varepsilon _0}{R^2}}}\). If at the highest position of the particle, the tension of the string just vanishes, the horizontal velocity at the lowest point has to be

A

0

B

\(2\sqrt {gR}\)

C

\(\sqrt {2gR}\)

D

\(\sqrt {5gR}\)

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6

2017 · Physics · Electricity · Electrostatics

WB JEE 2017

A charge of 0.8 coulomb is divided into two charges Q₁ and Q₂. These are kept at a separation of 30 cm. The force on Q₁ is maximum when

A

Q₁ = Q₂ = 0.4 C

B

Q₁ \(\approx\) 0.8 C, Q₂ negligible

C

Q₁ negligible, Q₂ \(\approx\) 0.8 C

D

Q₁ = 0.2 C, Q₂ = 0.6 C

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7

2017 · Physics · Electricity · Electrostatics

WB JEE 2017

A unit negative charge with mass M resides at the mid-point of the straight line of length 2a adjoining two fixed charges of magnitude +Q each. If it is given a very small displacement x(x << a) in a direction perpendicular to the straight line, it will

A

come back to its original position and stay there

B

execute oscillations with frequency \({1 \over {2\pi }}\sqrt {{Q \over {2\pi {\varepsilon _0}M{a^3}}}}\)

C

fly to infinity

D

execute oscillations with frequency \({1 \over {2\pi }}\sqrt {{Q \over {2\pi {\varepsilon _0}M{a^2}}}}\)

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8

2018 · Physics · Electricity · Electrostatics

WB JEE 2018

Consider a region in free space bounded by the surfaces of an imaginary cube having sides of length a as shown in the figure. A charge + Q is placed at the centre O of the cube. P is such a point outside the cube that the line OP perpendicularly intersects the surface ABCD at R and also OR = RP = a/2. A charge + Q is placed at point P also. What is the total electric flux through the five faces of the cube other than ABCD?

A

\({Q \over {{\varepsilon _0}}}\)

B

\({5Q \over {{6\varepsilon _0}}}\)

C

\({10Q \over {{6\varepsilon _0}}}\)

D

zero

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9

2018 · Physics · Electricity · Electrostatics

WB JEE 2018

Four equal charges of value + Q are placed at any four vertices of a regular hexagon of side 'a'. By suitably choosing the vertices, what can be maximum possible magnitude of electric field at the centre of the hexagon?

A

\({Q \over {4\pi {\varepsilon _0}{a^2}}}\)

B

\({{\sqrt 2 Q} \over {4\pi {\varepsilon _0}{a^2}}}\)

C

\({{\sqrt 3 Q} \over {4\pi {\varepsilon _0}{a^2}}}\)

D

\({{2Q} \over {4\pi {\varepsilon _0}{a^2}}}\)

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10

2018 · Physics · Electricity · Electrostatics

WB JEE 2018

The bob of a pendulum of mass m, suspended by an inextensible string of length L as shown in the figure carries a small charge q. An infinite horizontal plane conductor with uniform surface charge density \(\sigma\) is placed below it. What will be the time period of the pendulum for small amplitude oscillations?

A

\(2\pi \sqrt {{L \over {\left( {g - {{mq} \over {{\varepsilon _0}\sigma }}} \right)}}}\)

B

\(\sqrt {{L \over {\left( {g - {{mq\sigma } \over {{\varepsilon _0}}}} \right)}}}\)

C

\({1 \over {2\pi }}\sqrt {{L \over {\left( {g - {{q\sigma } \over {{\varepsilon _0}m}}} \right)}}}\)

D

\(2\pi \sqrt {{L \over {\left( {g - {{q\sigma } \over {{\varepsilon _0}m}}} \right)}}}\)

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11

2018 · Physics · Electricity · Electrostatics

WB JEE 2018

Two positive charges Q and 4Q are placed at points A and B respectively, where B is at a distance d units to the right of A. The total electric potential due to these charges is minimum at P on the line through A and B. What is (are) the distance (s) of P from A?

A

\({d \over 3}\) units to the right of A

B

\({d \over 3}\) units to the left of A

C

\({d \over 5}\) units to the right of A

D

d units to the left of A

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12

2018 · Physics · Electricity · Electrostatics

WB JEE 2018

A point charge \(-\) q is carried from a point A to another point B on the axis of a charged ring of radius r carrying a charge + q. If the point A is at a distance \({4 \over 3}r\) from the centre of the ring and the point B is \({3 \over 4}r\) from the centre but on the opposite side, what is the net work that need to be done for this?

A

\(- {7 \over 5}\,.\,{{{q^2}} \over {4\pi {\varepsilon _0}r}}\)

B

\(- {1 \over 5}\,.\,{{{q^2}} \over {4\pi {\varepsilon _0}r}}\)

C

\({7 \over 5}\,.\,{{{q^2}} \over {4\pi {\varepsilon _0}r}}\)

D

\({1 \over 5}\,.\,{{{q^2}} \over {4\pi {\varepsilon _0}r}}\)

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13

2019 · Physics · Electricity · Electrostatics

WB JEE 2019

A negative charge is placed at the midpoint between two fixed equal positive charges, separated by a distance 2d. If the negative charge is given a small displacement x(x < < d) perpendicular to the line joining the positive charges, how the force (F) developed on it will approximately depend on x?

A

F \(\propto\) x

B

\(F \propto {1 \over x}\)

C

F \(\propto\) x²

D

\(F \propto {1 \over {{x^2}}}\)

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14

2019 · Physics · Electricity · Electrostatics

WB JEE 2019

Eleven equal point charges, all of them having a charge +Q, are placed at all the hour positions of a circular clock of radius r, except at the 10 h position. What is the electric field strength at the centre of the clock?

A

\({Q \over {4\pi {\varepsilon _0}{r^2}}}\) from the centre towards the mark 10

B

\({Q \over {4\pi {\varepsilon _0}{r^2}}}\) from the mark 10 towards the centre

C

\({Q \over {4\pi {\varepsilon _0}{r^2}}}\) from the centre towards the mark 6

D

Zero.

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15

2020 · Physics · Electricity · Electrostatics

WB JEE 2020

As shown in the figure, a point charge q₁ = + 1 \(\times\) 10^-6 C is placed at the origin in xy-plane and another point charge q₂ = + 3 \(\times\) 10^-6 C is placed at the coordinate (10, 0).


In that case, which of the following graph(s) shows most correctly the electric field vector in E_x in x-direction?

A

B

C

D

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16

2020 · Physics · Electricity · Electrostatics

WB JEE 2020

Four identical point masses, each of mass m and carrying charge + q are placed at the corners of a square of sides a on a frictionless plane surface. If the particles are released simultaneously, the kinetic energy of the system when they are infinitely far apart is

A

\({{{q^2}} \over a}(2\sqrt 2 + 1)\)

B

\({{{q^2}} \over a}(\sqrt 2 + 2)\)

C

\({{{q^2}} \over a}(\sqrt 2 + 4)\)

D

\({{{q^2}} \over a}(\sqrt 2 + 1)\)

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17

2020 · Physics · Electricity · Electrostatics

WB JEE 2020

Two pith balls, each carrying charge + q are hung from a hook by two springs. It is found that when each charge is tripled, angle between the strings double. What was the initial angle between the strings?

A

30\(^\circ\)

B

60\(^\circ\)

C

45\(^\circ\)

D

90\(^\circ\)

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18

2020 · Physics · Electricity · Electrostatics

WB JEE 2020

A pair of parallel metal plates are kept with a separation d. One plate is at a potential + V and the other is at ground potential. A narrow beam of electrons enters the space between the plates with a velocity v₀ and in a direction parallel to the plates. What will be the angle of the beam with the plates after it travels an axial distance L?

A

\({\tan ^{ - 1}}\left( {{{eVL} \over {md{v_0}}}} \right)\)

B

\({\tan ^{ - 1}}\left( {{{eVL} \over {mdv_0^2}}} \right)\)

C

\({\sin ^{ - 1}}\left( {{{eVL} \over {md{v_0}}}} \right)\)

D

\({\cos ^{ - 1}}\left( {{{eVL} \over {mdv_0^2}}} \right)\)

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19

2020 · Physics · Electricity · Electrostatics

WB JEE 2020

A very long charged solid cylinder of radius a contains a uniform charge density p. Dielectric constant of the material of the cylinder is K. What will be the magnitude of electric field at a radial distance x (x < a) from the axis of the cylinder?

A

\(p{x \over {{\varepsilon _0}}}\)

B

\(p{x \over {{2k\varepsilon _0}}}\)

C

\(p{{{x^2}} \over {2a{\varepsilon _0}}}\)

D

\(p{{{x^{}}} \over {2k}}\)

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20

2021 · Physics · Electricity · Electrostatics

WB JEE 2021

The variation of electric field along the Z-axis due to a uniformly charged circular ring of radius a in XY-plane as shown in the figure. The value of coordinate M will be

A

\({1 \over 2}\)

B

\(\sqrt 2\)

C

1

D

\({1 \over {\sqrt 2 }}\)

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