NEET > Electrostatics

Explore popular questions from Electrostatics for NEET. This collection covers Electrostatics previous year NEET questions hand picked by popular teachers.


Q 1.    

Correct4

Incorrect-1

Two equally charged, identical metal spheres A and B repel each other with a force ‘F’. The spheres are kept fixed with a distance ‘r’ between them. A third identical, but uncharged sphere C is brought in contact with A and then placed at the mid point of the line joining A and B. The magnitude of the net electric force on C is

F

B

{tex} \frac { 3 \mathrm { F } } { 4 } {/tex}

C

{tex} \frac { \mathrm { F } } { 2 } {/tex}

D

{tex} \frac { \mathrm { F } } { 4 } {/tex}

Explanation



Q 2.    

Correct4

Incorrect-1

{tex} \mathrm { ABC } {/tex} is an equilateral triangle. Charges {tex} + \mathrm { q } {/tex} are placed at each corner as shown in fig. The electric intensity at centre O will be

A

{tex} \frac { 1 } { 4 \pi \epsilon _ { \mathrm { o } } } \frac { \mathrm { q } } { \mathrm { r } } {/tex}

B

{tex} \frac { 1 } { 4 \pi \epsilon _ { 0 } } \frac { q } { r ^ { 2 } } {/tex}

C

{tex} \frac { 1 } { 4 \pi \epsilon _ { 0 } } \frac { 3 q } { r ^ { 2 } } {/tex}

zero

Explanation

Q 3.    

Correct4

Incorrect-1

An electric dipole is placed in a uniform electric field. The dipole will experience

A

a force that will displace it in the direction of the field

B

a force that will displace it in a direction opposite to the field.

a torque which will rotate it without displacement

D

a torque which will rotate it and a force that will displace it

Explanation

Q 4.    

Correct4

Incorrect-1

Which one of the following graphs represents the variation of electric field with distance r from the centre of a charged spherical conductor of radius {tex} \mathrm { R } ? {/tex}

A

B

D

Explanation

Q 5.    

Correct4

Incorrect-1

If {tex} E _ { a } {/tex} be the electric field strength of a short dipole at a point on its axial line and {tex} E _ { \mathrm { c } } {/tex} that on the equatorial line at the same distance, then

A

{tex} E _ { e } = 2 E _ { q } {/tex}

{tex} E _ { a } = 2 E _ { e } {/tex}

C

{tex} E _ { a } = E _ { e } {/tex}

D

None of the above

Explanation

Q 6.    

Correct4

Incorrect-1

Three positive charges of equal value {tex} q {/tex} are placed at vertices of an equilateral triangle. The resulting lines of force should be sketched as in

A

B

D

Explanation



Q 7.    

Correct4

Incorrect-1

Point charges {tex} + 4 q , - q {/tex} and {tex} + 4 q {/tex} are kept on the {tex} X {/tex} -axis at points {tex} x = 0 , x = a {/tex} and {tex} x = 2 a {/tex} respectively.

A

only {tex} - q {/tex} is in stable equilibrium

B

none of the charges is in equilibrium

all the charges are in unstable equilibrium

D

all the charges are in stable equilibrium.

Explanation

Q 8.    

Correct4

Incorrect-1

Two charge {tex} q {/tex} and {tex} - 3 q {/tex} are placed fixed on {tex} x {/tex} -axis separated by distance {tex} d . {/tex} Where should a third charge 2{tex} q {/tex} be placed such that it will not experience any force?

A

{tex} \frac { d - \sqrt { 3 } d } { 2 } {/tex}

{tex} \frac { d + \sqrt { 3 } d } { 2 } {/tex}

C

{tex} \frac { d + 3 d } { 2 } {/tex}

D

{tex} \frac { d - 3 d } { 2 } {/tex}

Explanation

Q 9.    

Correct4

Incorrect-1

An oil drop of radius {tex} \mathrm { r } {/tex} and density {tex} \rho {/tex} is held stationary in a uniform vertically upwards electric field 'E' If {tex} \rho _ { 0 } ( < \rho ) {/tex} is the density of air and {tex} \mathrm { e } {/tex} is quanta of charge, then the drop has-

A

{tex} \frac { 4 \pi ^ { 3 } \left( \rho - \rho _ { 0 } \right) \mathrm { g } } { 3 \mathrm { eE } } {/tex} excess electrons

B

{tex} \frac { 4 \pi r ^ { 2 } \left( \rho - \rho _ { 0 } \right) g } { e E } {/tex} excess electrons

deficiency of {tex} \frac { 4 \pi \mathrm { r } ^ { 3 } \left( \mathrm { p } - \mathrm { P } _ { 0 } \right) \mathrm { g } } { 3 \mathrm { eE } } {/tex} electron

D

deficiency of {tex} \frac { 4 \pi r ^ { 2 } \left( \rho - \rho _ { 0 } \right) g } { \mathrm { eE } } {/tex} electrons

Explanation

Q 10.    

Correct4

Incorrect-1

A square surface of side {tex} L {/tex} meter in the plane of the paper is placed in a uniform electric field {tex} E ( \text { volt } / \mathrm { m } \text { ) acting along the } {/tex} same plane at an angle {tex} \theta {/tex} with the horizontal side of the square as shown in Figure. The electric flux linked to the surface, in units of volt. {tex} m , {/tex} is

A

{tex} \mathrm { EL } ^ { 2 } {/tex}

B

{tex} \mathrm { EL } ^ { 2 } \cos \theta {/tex}

C

{tex} \mathrm { EL } ^ { 2 } \sin \theta {/tex}

zero

Explanation

Q 11.    

Correct4

Incorrect-1

If n drops, each charged to a potential V, coalesce to form a single drop. The potential of the big drop will be

A

{tex} \frac { V } { n ^ { 2 / 3 } } {/tex}

B

{tex} \frac { \mathrm { V } } { \mathrm { n } ^ { 1 / 3 } } {/tex}

C

{tex} \mathrm { Vn } ^ { 1 / 3 } {/tex}

{tex} \mathrm { Vn } ^ { 2 / 3 } {/tex}

Explanation

Q 12.    

Correct4

Incorrect-1

The capacitance of a parallel plate capacitor is C{tex}_a{/tex} (Fig. a). A dielectric of dielectric constant K is inserted as shown in fig. (b) and (c). If C{tex}_b{/tex} and C{tex}_c{/tex} denote the capacitance in fig. (b) and (c), then

both {tex} \mathrm { C } _ { \mathrm { b } } , \mathrm { C } _ { \mathrm { c } } > \mathrm { C } _ { \mathrm { a } } {/tex}

B

{tex} \mathrm { C } _ { \mathrm { c } } > \mathrm { C } _ { \mathrm { a } } {/tex} while {tex} \mathrm { C } _ { \mathrm { b } } > \mathrm { C } _ { \mathrm { a } } {/tex}

C

{tex} \operatorname { both } \mathrm { C } _ { \mathrm { b } } , \mathrm { C } _ { \mathrm { c } } < \mathrm { C } _ { \mathrm { a } } {/tex}

D

{tex} C _ { a } = C _ { b } = C _ { c } {/tex}

Explanation

Q 13.    

Correct4

Incorrect-1

What is the effective capacitance between X and Y?

A

24{tex} \mu F {/tex}

B

18{tex} \mu F {/tex}

C

12{tex} \mu F {/tex}

6{tex} \mathrm { u } \mathrm { W } {/tex}

Explanation

Q 14.    

Correct4

Incorrect-1

There exists a non!-uniform electric field along {tex} \mathrm { x } {/tex} -axis as shown in the figure below. The field increases at a uniform rate along {tex} + \mathrm { ve } {/tex} x-axis. A dipole is placed inside the field as shown. Which one of the following is correct for the dipole?

A

Dipole moves along positive {tex} x {/tex} -axis and undergoes a clockwise rotation

B

Dipole moves along negative {tex} \mathrm { x } {/tex} -axis and undergoes a clockwise rotation

C

Dipole moves along positive {tex} \mathrm { x } {/tex} -axis and undergoes a anticlockwise rotation

Dipole moves along negative {tex} x {/tex} -axis and undergoes a anticlockwise rotation

Explanation

Q 15.    

Correct4

Incorrect-1

A

{tex} E L ^ { 2 }/2 {/tex}

zero

C

{tex} E L ^ { 2 } {/tex}

D

{tex} E L ^ { 2 } / \left( 2 \varepsilon _ { 0 } \right) {/tex}

Explanation

Q 16.    

Correct4

Incorrect-1

A

{tex} \frac { \varepsilon _ { 0 } \mathrm { A } } { \mathrm { d } } {/tex}

{tex} \frac { 2 \varepsilon _ { 0 } \mathrm { A } } { \mathrm { d } } {/tex}

C

{tex} \frac { 3 \varepsilon _ { 0 } \mathrm { A } } { \mathrm { d } } {/tex}

D

{tex} \frac { 4 \varepsilon _ { 0 } \mathrm { A } } { \mathrm { d } } {/tex}

Explanation

Q 17.    

Correct4

Incorrect-1

If a slab of insulating material {tex} 4 \times 10 ^ { - 5 } \mathrm { m } {/tex} thick is introduced between the plates of a parallel plate capacitor, the distance between the plates has to be increased by {tex} 3.5 \times 10 ^ { - 5 } \mathrm { m } {/tex} to restore the capacity to original value. Then the dielectric constant of the material of slab is

8

B

6

C

12

D

10

Explanation

Q 18.    

Correct4

Incorrect-1

A unit charge moves on an equipotential surface from a point {tex} \mathrm { A } {/tex} to point {tex} \mathrm { B } {/tex} , then

A

{tex} \mathrm { V } _ { \mathrm { A } } - \mathrm { V } _ { \mathrm { B } } = + \mathrm { ve } {/tex}

{tex} V _ { A } - V _ { B } = 0 {/tex}

C

{tex} \mathrm { V } _ { \mathrm { A } } - \mathrm { V } _ { \mathrm { B } } = - \mathrm { ve } {/tex}

D

it is stationary

Explanation



Q 19.    

Correct4

Incorrect-1

If the electric flux entering and leaving a closed surface are {tex} 6 \times 10 ^ { 6 } {/tex} and {tex} 9 \times 10 ^ { 6 } {/tex} S.I. units respectively, then the charge inside the surface of permittivity of free space {tex} \varepsilon _ { 0 } {/tex} is

A

{tex} \varepsilon _ { 0 } \times 10 ^ { 6 } {/tex}

B

{tex} - \varepsilon _ { 0 } \times 10 ^ { 6 } {/tex}

C

{tex} - 2 \varepsilon _ { 0 } \times 10 ^ { 6 } {/tex}

{tex} 3 \varepsilon _ { 0 } \times 10 ^ { 6 } {/tex}

Explanation

Q 20.    

Correct4

Incorrect-1

Identify the false statement.

A

Inside a charged or neurral conductor, electrostatic field is zero

The electrostatic field at the surface of the charged conductor must be tangential to the surface at any point

C

There is no net charge at any point inside the conductor

D

Electrostatic potential is constant throughout the volume of the conductor

Explanation

Q 21.    

Correct4

Incorrect-1

An air capacitor {tex} \mathrm { C } {/tex} connected to a battery of e. {tex} \mathrm { m } . {/tex} {tex} \mathrm { f } .\ {/tex} V acquires a charge {tex} \mathrm { q } {/tex} and energy {tex} \mathrm { E } {/tex} . The capacitor is disconnected from the battery and a dielectric slab is placed between the plates. Which of the following statements is correct?

A

{tex} \mathrm { V } {/tex} and {tex} \mathrm { q } {/tex} decrease but {tex} \mathrm { C } {/tex} and {tex} \mathrm { E } {/tex} increase

B

V remains unchange, but {tex} \mathrm { q } , \mathrm { E } {/tex} and {tex} \mathrm { C } {/tex} increase

q remains unchanged, C increases, V and E decrease

D

{tex} \mathrm { q } {/tex} and {tex} \mathrm { C } {/tex} increase but {tex} \mathrm { V } {/tex} and {tex} \mathrm { E } {/tex} decrease.

Explanation


Q 22.    

Correct4

Incorrect-1

Choose the wrong statement about equipotential surfaces.

A

It is a surface over which the potential is constant

The electric field is parallel to the equipotential surface

C

The electric field is perpendicular to the equipotential surface

D

The electric field is in the direction of stecpest decrease of potential

Explanation

Q 23.    

Correct4

Incorrect-1

Two spherical conductors {tex} A {/tex} and {tex} B {/tex} of radii a and {tex} b {/tex} (b/>a) are placed concentrically in air. The two are connected by a copper wire as shown in figure. Then the equivalent capacitance of the system is

A

4{tex} \pi \varepsilon _ { 0 } \frac { \mathrm { ab } } { \mathrm { b } - \mathrm { a } } {/tex}

B

4{tex} \pi \varepsilon _ { 0 } ( a + b ) {/tex}

4{tex} \pi \varepsilon _ { 0 } b {/tex}

D

4{tex} \pi \varepsilon _ { 0 } \mathrm { a } {/tex}

Explanation

Q 24.    

Correct4

Incorrect-1

Which of the following figure shows the correct equipotential surfaces of a system of two positive charges?

A

B

D

Explanation

Q 25.    

Correct4

Incorrect-1

In a given network the equivalent capacitance between {tex} A {/tex} and {tex} B {/tex} is {tex} \left[ C _ { 1 } = C _ { 4 } = \right. {/tex} {tex} \left. 1 \mu F , C _ { 2 } = C _ { 3 } = 2 \mu F \right] {/tex}

3{tex} \mu F {/tex}

B

6{tex} \mu F {/tex}

C

4.5{tex} \mu F {/tex}

D

2.5{tex} \mu F {/tex}

Explanation