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The force between two identical charges placed at a distance of $r$ in a vacuum is $F$ . Now a slab of dielectric constant $4$ is inserted between these two charges. If the thickness of the slab is $\frac{r}{2}$ , then the force between the charges will become

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Important Questions on Electric Charges and Fields

MEDIUM

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

A simple pendulum of length

L

is placed between the plates of a parallel plate capacitor having electric field

E

, as shown in figure. Its bob has mass

m

and charge

q

. The time period of the pendulum is given by:
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EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

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>Coulomb's Laws

A wire of resistance

R

is bent to form a square

A B C D

as shown in the figure. The effective resistance between

E

and

C

is:
(

E

is mid-point of arm

C D

)

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

Amongst the following, the form of water with the lowest ionic conductance at

298 K

is:

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

A charged particle initially at rest at

O

, when released follows a trajectory as shown. Such a trajectory is possible in the presence of
Question Image

HARD

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

Three charged particles $A, B$ and $C$ with charges $- 4 q, 2 q$ and $- 2 q$ are present on the circumference of a circle of radius $d .$ The charged particles $A, C$ and centre $O$ of the circle formed an equilateral triangle as shown in the figure. The electric field at the point $O$ is
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EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

The bob of a simple pendulum has mass

2 g

and a charge of

5.0 μ C .

It is at rest in a uniform horizontal electric field of intensity

2000 V / m

At equilibrium, the angle that the pendulum makes with the vertical is:

(t a k e g = 10 m / s^{2})

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

Which of the following is a landlocked country?

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

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>Electric Charges and Fields>Coulomb's Laws

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>Electric Charges and Fields>Coulomb's Laws

An electric current of

0.5 A

is passed for

8

minutes through the filament of an electric bulb. What will be the charge passing through the medium of the electric current?

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

Two metal wires of identical dimensions are connected in series. If

v_{1}

and

v_{2}

are the conductivities of the metal wires respectively, the effective conductivity if the combination is:

MEDIUM

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

The commonly used safety fuse-wire is made up of _____.

HARD

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

A particle of mass

m

and charge

q

is released from rest in a uniform electric field. If there is no other force on the particle, the dependence of its speed

v

on the distance

x

travelled by it is correctly given by (graphs are schematic and not drawn to scale)

MEDIUM

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

What will be the direction of the magnetic field at the very bottom point of a horizontal power line, where the current flows from east to west when viewed from the west end?

MEDIUM

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

A particle of mass

m

and charge

q

is placed at rest in uniform electric field

E

and then released. The kinetic energy attained by the particle after moving a distance

y

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

On which lake is the Golden Temple located?

EASY

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

The flow of _____ is anti–clockwise in the given circuit:

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HARD

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

Two positively charged spheres of masses

m_{1} and m_{2}

are suspended from a common point at the ceiling by identical insulating massless strings of length

l

. Charges on the two spheres are

q_{1} and q_{2}

, respectively. At equilibrium, both strings make the same angle

θ

with the vertical. Then

HARD

Physics>Electricity and Magnetism>Electric Charges and Fields>Coulomb's Laws

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

The force between two identical charges placed at a distance of r in a vacuum is F. Now a slab of dielectric constant 4 is inserted between these two charges. If the thickness of the slab is r 2, then the force between the charges will become

Important Questions on Electric Charges and Fields

Learn and Prepare for any exam you want !

The force between two identical charges placed at a distance of $r$ in a vacuum is $F$ . Now a slab of dielectric constant $4$ is inserted between these two charges. If the thickness of the slab is $\frac{r}{2}$ , then the force between the charges will become