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An electron and a proton are moving under mutual attractive forces. For calculating the change in kinetic energy of the system during motion, the magnetic force of one another is neglected because the magnetic forces

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Important Questions on Electric Charges and Fields

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

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>Electric Field

A charged particle initially at rest at

O

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

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

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

HARD

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

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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MEDIUM

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

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}]

MEDIUM

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

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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MEDIUM

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

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.

HARD

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

A charged particle (mass $m$ and charge $q$ ) moves along $X$ axis with velocity $V_{0}$ . When it passes through the origin it enters a region having uniform electric field $\vec{E} = - E \hat{j}$ which extends upto $x = d$ . Equation of path of electron in the region $x > d$ is:

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HARD

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

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>Electric Charges and Fields>Electric Field

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>Electric Charges and Fields>Electric Field

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)

HARD

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

An electron falls from rest through a vertical distance

h

in a uniform and vertically upward directed electric field

E

. The direction of electric filed is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance

h

. The time of fall of the electron, in comparison to the time of fall of the proton is

MEDIUM

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

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

HARD

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

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:

EASY

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

Two charged thin infinite plane sheets of uniform charge density

σ_{+}

and

σ_{-}

, where

|σ_{+}| > |σ_{-}|

, intersect at the right angle. Which of the following best represents the electric field lines for the system:

MEDIUM

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

Suppose that intensity of a laser is

(\frac{315}{π}) W m^{- 2} .

The rms electric field, in units of

V m^{- 1}

associated with this source is close to the nearest integer is

- (ε_{0} = 8.86 \times 10^{- 12} C^{2} N m^{- 2}; c = 3 \times 10^{8} m s^{- 1})

EASY

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

Charges $Q_{1}$ and $Q_{2}$ are at points $A$ and $B$ of a right-angled triangle $O A B$ . The resultant electric field at point $O$ is perpendicular to the hypotenuse, then $Q_{1} / Q_{2}$ is proportional to:

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EASY

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

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>Electric Charges and Fields>Electric Field

A toy car with charge q moves on a frictionless horizontal plane surface under the influence of a uniform electric field

\vec{E}

. Due to the force

q \vec{E}

, its velocity increases from 0 to

6 m s^{- 1}

in one second duration. At that instant the direction of the field is reversed. The car continues to move for two more seconds under the influence of this field. The average velocity and the average speed of the toy car between

0

3

seconds are respectively

EASY

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

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?

An electron and a proton are moving under mutual attractive forces. For calculating the change in kinetic energy of the system during motion, the magnetic force of one another is neglected because the magnetic forces

Important Questions on Electric Charges and Fields

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