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A charge $q$ is placed at the centre of the line joining two equal charges $Q .$ The system of the three charges will be in equilibrium if $q$ is equal to

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Important Questions on Electrostatics

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Three Point charges each equal to

+ q

are placed at the vertices of an equilateral triangle of side

' l'

. The net force on a charge

q_{1}

placed at the centre of the triangle is

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

The acceleration of an electron due to the mutual attraction between the electron and a proton when they are

1.6 Å

apart is,

(m_{e} ≃ 9 \times 10^{- 31} kg, e = 1.6 \times 10^{- 19} C)

(Take

\frac{1}{4 π ε_{0}} = 9 \times 10^{9} N m^{2} C^{- 2}

)

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Two small metal spheres

A

and

B

charged positively are separated by

2 m

in air. The force on a charge of

+ 1 C

placed on the line joining the centres of the spheres and at a distance of

0.5 m

from

A

is found to be zero. The ratio

q_{A} : q_{B}

of charges on

A

and

B

HARD

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

A negative charge is placed at the midpoint between two fixed equal positive charges, separated by a distance $2 d$ . 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 $x$ ?

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Suppose the charge of a proton and an electron differ slightly. One of them is

e

, the other is

(e + Δ e)

. If the net electrostatic force and gravitational force between two hydrogen atoms placed at a distance

d

(much greater than atomic size) apart is zero, then

Δ e

is of the order of [Given mass of hydrogen

m_{h} = 1.67 \times 10^{- 27} kg

]

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Two equally charged metal spheres

A

and

B

repel each other with a force of

4 \times 10^{- 5} N

. Another identical uncharged sphere

C

is touched to

A

and then placed at the mid point of the line joining the spheres

A

and

B

. The net electric force on the sphere

C

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Two electrons are moving with equal speed of

5 \times 10^{5} m s^{- 1}

parallel to each other. The ratio of the electrostatic to the magnetic force between them is

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Three identical charges are placed on three vertices of a square. If the force acting between

q_{1}

and

q_{2}

F_{12}

and between

q_{1}

and

q_{3}

F_{13}

then

\frac{F_{13}}{F_{12}} =

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Two charges of equal magnitudes and at a distance $r$ exert a force $F$ on each other. If the charges are halved and distance between them is doubled, then the new force acting on each charge is

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Two point charges A and B, having charges

+ Q

and

- Q

respectively, are placed at certain distance apart and force acting between them is

F

. If

25 %

charge of

A

is transferred to

B

, then the force between the charges becomes

HARD

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Two pith balls, each carrying charge

+ q

are hung from a hook by two strings. It is found that when each charge is tripled, angle between the strings double. What was the initial angle between the strings?

HARD

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Two charges, each equal to

q

, are kept at

x = - a

and

x = a

on the x-axis. A particle of mass

m

and charge

q_{0} = - \frac{q}{2}

is placed at the origin. If charge

q_{0}

is given a small displacement

(y ≪ a)

along the y-axis, the net force acting on the particle is proportional to :

HARD

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

The force of repulsion between two identical positive charges when kept, with a separation '

r

' in the air is '

F

'. Half the gap between the two charges is filled by a dielectric slab of dielectric constant

= 4

. Then, the new force of repulsion between those two charges becomes

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Three identical charges each of magnitude

3 μ C

are placed at the corners of a right angled triangle

ABC

whose base

B C

and height

B A

are

3 cm

and

4 cm

respectively. Forces on the charge at right angled corner

B

due to charges at

A

and

C

are

F_{1}

and

F_{2}

respectively. The angle between their resultant force and

F_{2}

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

A charge

Q

is placed at the centre of the line joining two equal charges

q

. The system of the three charges will be in equilibrium if

Q

is equal to

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Two equal point charges of $1 μ C$ each are located at points $(\hat{i} + \hat{j} + \hat{k}) m$ and $(2 \hat{i} + 3 \hat{j} - \hat{k}) m$ . What is the magnitude of electrostatic force between them?

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

The electric force acting between two point charges kept at a certain distance in vacuum is

16 N .

If the same two charges are kept at the same distance in a medium of dielectric constant

8 .

The electric force acting between them is _____

HARD

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

A certain charge

2 Q

is divided at first into two parts

q_{1}

and

q_{2}

. Later the charges are placed at a certain distance. If the force of interaction between two charges is maximum then

\frac{Q}{q_{1}} =

EASY

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

The dimensional formula of coefficient of permittivity for free space (

ε_{0}

) in the equation

F = \frac{1}{4 π ε_{0}} \frac{q_{1} q_{2}}{r^{2}},

where symbols have their usual meanings, is

HARD

Physics>Electricity and Magnetism>Electrostatics>Coulomb's Law

Two identical charged spheres suspended from a common point by two massless strings of lengths

l

, are initially at a distance

d (d ≪ l)

apart because of their mutual repulsion. The charges begin to leak from both the spheres at a constant rate. As a result, the spheres approach each other with a velocity

υ

. Then

υ

varies as a function of the distance

x

between the spheres, as

A charge q is placed at the centre of the line joining two equal charges Q . The system of the three charges will be in equilibrium if q is equal to

Important Questions on Electrostatics

Learn and Prepare for any exam you want !

A charge $q$ is placed at the centre of the line joining two equal charges $Q .$ The system of the three charges will be in equilibrium if $q$ is equal to