An infinite line charge produces an electric field of 1 . 8 × 10 5 N C - 1 at a distance of 2 cm . Calculate the linear charge density.

Given, The electric field produced by the infinite linear charge E = 1 . 8 × 10 5 N C - 1 Distance at which electric field is calculated d = 2 cm = 2 × 10 - 2 m Electric field due to infinite linear charge at a distance d from it is E = λ 2 π ε ∘ d ⇒ λ = 2 π ε ∘ E d = 4 π ε ∘ E d 2 = 18 × 10 4 × 0 . 02 9 × 10 9 × 2 = 0 . 02 × 10 - 5 C m - 1 = 0 . 2 μ C m - 1 Hence, the linear charge density is 0 . 2 μ C m - 1 .

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All the statements given below are correct :

(A) Repulsion is sure test of electrification
(B) Two likely charged body may attract each other
(C) Electroscope is used to detect charge on object
(D) Electric force between $2$ point charges does not depends on nearer bodies

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Important Questions on Electric Charges and Fields

MEDIUM

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

A length - scale

(l)

depends on the permittivity

(ε)

of a dielectric material, Boltzmann constant

k_{B}

, the absolute temperature T, the number per unit volume (n) of certain charged particles, and the charge (q) carried by each of the particles, Which of the following expressions (s) for

l

is (are) dimensionally correct?

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

The dimensional formula of charge is _____.

HARD

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

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

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

Two identical conducting spheres

A

and

B

carry an equal charges. They are separated by a distance much larger than their diameters, and the force between them is

F

. A third identical conducting sphere,

C

, is uncharged. Sphere

C

is first touched to

A

, then to

B

, and then removed. As a result, the force between

A

and

B

would be equal to:

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

As shown in the figure, two particles, each of mass $' m'$ tied at the ends of a light string of length $2 a$ are kept on a frictionless horizontal surface. When the mid point $(P)$ of the string is pulled vertically upwards with a small but constant force $F,$ the particles move towards each other on the surface. Magnitude of acceleration of each particle, when the separation between them becomes $2 x$ is

Question Image

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

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

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

The attractive force results when a glass rod rubbed with a silk and a plastic rod rubbed with a fur brings together. During friction which type of charges are developed on glass rod and plastic rod?

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

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

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

The charge on one electron is :

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

An infinite line charge produces an electric field of

1.8 \times 10^{5} N C^{- 1}

at a distance of

2 cm

. Calculate the linear charge density.

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

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

]

MEDIUM

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

What are conductors? Give two examples.

MEDIUM

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

Three concentric metal shells

A, B

and

C

of respective radii

a, b

and

c (a < b < c)

have surface charge densities

+ σ, - σ

and

+ σ

respectively. The potential of shell

B

is:

HARD

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

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 :

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

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

HARD

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

Two isolated conducting spheres

S_{1}

and

S_{2}

of radius

\frac{2}{3} R

and

\frac{1}{3} R

have

12 μ C

and

- 3 μ C

charges, respectively, and are at a large distance from each other, They are now connected by a conducting wire. A long time after this is done the charges on

S_{1}

and

S_{2}

are respectively:

HARD

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

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>Electric Charges and Fields>Electric Charge

State the principle of conservation and principle of quantization of electric charge.

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

What is a conductor of electricity? Give two examples.

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Electric Charge

Why are metals good conductors of electricity whereas glass is a bad conductor of electricity? Give reason.

All the statements given below are correct : (A) Repulsion is sure test of electrification (B) Two likely charged body may attract each other (C) Electroscope is used to detect charge on object (D) Electric force between 2 point charges does not depends on nearer bodies

Important Questions on Electric Charges and Fields

Learn and Prepare for any exam you want !

All the statements given below are correct :

(A) Repulsion is sure test of electrification
(B) Two likely charged body may attract each other
(C) Electroscope is used to detect charge on object
(D) Electric force between $2$ point charges does not depends on nearer bodies