Match List ‐ I (Experiment performed) with List ‐ II (Phenomena discovered/associated)and select the correct option from the options given below the lists List-I List-II ( a ) Davisson and Germer experiment i Wave nature of electrons b Millikan's oil drop experiment ii Charge of an electron c Rutherford experiment iii Quantisation of energy levels d Franck-Hertz experiment ( iv ) Existence of the nucleus

( a ) ‐ ( i ) , ( b ) ‐ ( ii ) , ( c ) ‐ ( iv ) , ( d ) ‐ ( iii )

( a ) ‐ ( iii ) , ( b ) ‐ ( iv ) , ( c ) ‐ ( i ) , ( d ) ‐ ( ii )

( a ) ‐ ( iv ) , ( b ) ‐ ( iii ) , ( c ) ‐ ( ii ) , ( d ) ‐ ( i )

( a ) ‐ ( i ) , ( b ) ‐ ( ii ) , ( c ) ‐ ( iii ) , ( d ) ‐ ( iv )

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If the flux of the electric field through a closed surface is zero then

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Important Questions on Electrostatics

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

An electric field due to a positively charged long straight wire at a distance

r

from it is proportional to

r^{- 1}

in magnitude. Two electrons are orbiting such a long straight wire in circular orbits of radii

1 \overset{\circ}{A}

and

2 \overset{\circ}{A}

. The ratio of their respective time periods is

EASY

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

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

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

A total charge

q

is divide as

q_{1}

and

q_{2}

which are kept at two of the vertices of an equilateral triangle of side

a

. The magnitude of the electric field E at the third vertex of the triangle is to be depicted schematically as a function of

x = \frac{q_{1}}{q}

. Choose the correct figure.

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

Charges Q, 2Q and 4Q are uniformly distributed in three dielectric solid spheres 1, 2 and 3 of radii R/2, R and 2R respectively, as shown in the figure. If magnitudes of the electric fields at point P at a distance R from the centre of spheres 1, 2 and 3 are

E_{1}, E_{2}

and

E_{3}

respectively, then

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HARD

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

A particle, of mass

10^{- 3} kg

and charge

1.0 C

, is initially at rest. At time

t = 0

, the particle comes under the influence of an electric field

\vec{E} (t) = E_{0} \sin (ω t) \hat{i}

, where

E_{0} = 1.0 N C^{- 1}

and

ω = 10^{3} rad s^{- 1}

. Consider the effect of only the electrical force on the particle. Then the maximum speed, in

m s^{- 1}

, attained by the particle at subsequent times is ____________.

HARD

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

The figures below depict two situations in which two infinitely long static line charges of constant positive line charge density

λ

are kept parallel to each other. In their resulting electric field, point charges

q

and

- q

are kept in equilibrium between them. The point charges are confined to move in the

x

direction only. If they are given a small displacement about their equilibrium positions, then the correct statements(s) is (are)

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HARD

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

Two non-conducting solid spheres of radii $R$ and $2 R$ , having uniform volume charge densities $ρ_{1}$ and $ρ_{2}$ , respectively, touch each other. The net electric field at a distance $2 R$ from the centre of the smaller sphere, along the line joining the centres of the spheres, is zero. The ratio $\frac{ρ_{1}}{ρ_{2}}$ can be

HARD

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

Four point charges

- q, + q, + q

and

- q

are placed on y-axis at

y = - 2 d, y = - d,

and

y = + 2 d,

respectively. The magnitude of the electric field

E

at a point on the x-axis at

x = D,

with

D ≫ d,

will behave as:

HARD

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

A thin disc of radius $b = 2 a$ has a concentric hole of radius $a$ in it (see figure). It carries uniform surface charge $σ$ on it. If the electric field on its axis at a height $h (h < < a)$ from its centre is given as $C h$ then the value of $C$ is

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HARD

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

A wire of length

L = 20 c m

is bent into a semi-circular arc and the two equal halves of the arc are uniformly charged with charges

+ Q

and

- Q

as shown in the figure. The magnitude of the charge on each half is

|Q| = 10^{3} ε_{0}

, where

ε_{0}

is the permittivity of free the space. The net electric field at the centre

O

EASY

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

A hollow metal sphere of radius

R

is uniformly charged. The electric field due to the sphere at a distance

r

from the center

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

A metallic sphere is placed in a uniform electric field. The line of force follow the path(s) shown in the figure as,

Question Image

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

Two parallel infinite line charges with linear charge densities

+ λ C m^{- 1}

and

- λ C m^{- 1}

are placed at a distance of

2 R

in free space. What is the electric field mid-way between the two-line charges?

EASY

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

Match List $‐ I$ (Experiment performed) with List $‐ II$ (Phenomena discovered/associated)and select the correct option from the options given below the lists

	List-I		List-II
$(a)$	Davisson and Germer experiment	$(i)$	Wave nature of electrons
$(b)$	Millikan's oil drop experiment	$(ii)$	Charge of an electron
$(c)$	Rutherford experiment	$(iii)$	Quantisation of energy levels
$(d)$	Franck-Hertz experiment	$(iv)$	Existence of the nucleus

EASY

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

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})

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

A conducting sphere of radius

R

is given a charge

Q .

The electric potential and the electric field at the center of the sphere respectively are:

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

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:
Question Image

EASY

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

The electric field in a certain region is acting radially outward and is given by

E = A r

. A charge contained in a sphere of radius

a

centred at the origin of the field will be given by

MEDIUM

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

Two point charges

q_{1} (\sqrt{10} μC)

and

q_{2} (- 25 μC)

are placed on the

x

-axis at

x = 1 m

and

x = 4 m

respectively. The electric field

(in V m^{- 1})

at a point

y = 3 m

y

-axis is,

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

EASY

Physics>Electricity and Magnetism>Electrostatics>Electric Field (Discrete and Continuous Charge Distributions)

In Millikan's oil drop experiment, the forces acting on the oil drop are?

If the flux of the electric field through a closed surface is zero then

Important Questions on Electrostatics

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