Electric Charges and Fields Set-2

Test your knowledge on Electric Charges and Fields from Physics, Class 12.

Minutes

Questions

1 / -0

Marking Scheme

Don't have an account? Sign up for free to save your progress and track your history.

Questions in this Quiz

Q1: A cylinder of radius $r$ and length $l$ is placed in a uniform electric field parallel to the axis of the cylinder. The total flux for the surface of the cylinder is given by

zero
$\pi r^2 E$
$2 \pi r l E$
$2 \pi r^2 E$

Q2: Two parallel large thin metal sheets have equal surface charge densities $26.4 \times 10^{-12} \text{ C/m}^2$ of opposite signs. The electric field between these sheets is

$3 \times 10^{-10} \text{ N/C}$
$1.5 \times 10^{-10} \text{ N/C}$
$3 \text{ N/C}$
$1.5 \times 10^{10} \text{ N/C}$

Q3: A point charge situated at a distance '$r$' from a short electric dipole on its axis, experiences a force $\vec{F}$. If the distance of the charge is '$2r$', the force on the charge will be

$\vec{F}/16$
$\vec{F}/8$
$\vec{F}/4$
$\vec{F}/2$

Q4: The magnitude of the electric field due to a point charge at a distance of $4.0 \text{ m}$ is $9 \text{ N/C}$. From the same charged object the electric field of magnitude, $16 \text{ N/C}$ will be at a distance of

$1 \text{ m}$
$2 \text{ m}$
$3 \text{ m}$
$6 \text{ m}$

Q5: An electron experiences $\vec{F} = (1.6 \times 10^{-16} \text{ N}) \hat{i}$ in an electric field $\vec{E}$. The electric field is

$(1.0 \times 10^3 \text{ N/C}) \hat{i}$
$(-1.0 \times 10^3 \text{ N/C}) \hat{i}$
$(1.0 \times 10^{-3} \text{ N/C}) \hat{i}$
$(-1.0 \times 10^{-3} \text{ N/C}) \hat{i}$

Q6: Two charges $q_1$ and $q_2$ are placed at the centres of two spherical conducting shells of radii $r_1$ and $r_2$ respectively. The shells are arranged such that their centres are $d$ $[d > (r_1 + r_2)]$ apart. The force on $q_2$ due to $q_1$ is:

$\frac{1}{4\pi\epsilon_0} \frac{q_1 q_2}{d^2}$
$\frac{1}{4\pi\epsilon_0} \frac{q_1 q_2}{(d-r_1-r_2)^2}$
zero
$\frac{1}{4\pi\epsilon_0} \frac{q_1 q_2}{(r_1+r_2)^2}$

Q7: An electric dipole of length $2 \text{ cm}$ is placed at an angle of $30^\circ$ with an electric field of $2 \times 10^5 \text{ N/C}$. If the dipole experiences a torque of $8 \times 10^{-3} \text{ Nm}$, the magnitude of either charge of the dipole is,

$4 \mu \text{C}$
$7 \mu \text{C}$
$8 \mu \text{C}$
$2 \mu \text{C}$

Q8: Assertion (A): A negative charge in an electric field moves along the direction of the electric field.
Reason (R): On a negative charge a force acts in the direction of the electric field.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false and R is also false.

Q9: Assertion (A): Charge is quantized only integral number of electrons can be transferred.
Reason (R): There is no possibility of transfer of some fraction of electron.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false and R is also false.

Q10: Assertion (A): In a non-uniform electric field, a dipole will have translatory as well as rotatory motion.
Reason (R): In a non-uniform electric field, a dipole experiences a force as well as torque.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false and R is also false.

Q11: Assertion (A): Electrostatic field lines start at positive charges and end at negative charges. Reason (R): Field lines are continuous curves without any breaks and they form closed loop.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false and R is also false.

Q12: Assertion (A): Electrons moves away from a region of lower potential to a region of higher potential. Reason (R): An electron has a negative charge.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false and R is also false.

Q13: Assertion (A): All the charge in a conductor gets distributed on whole of its outer surface. Reason (R): In a dynamic system, charges try to keep their potential energy minimum.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false and R is also false.

Q14: Assertion (A): When a body acquires negative charge, its mass decreases. Reason (R): A body acquires positive charge when it gains electrons.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false and R is also false.

Q15: Assertion (A): Surface charge density of an irregularly shaped conductor is non-uniform. Reason (R): Surface density is defined as charge per unit area.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false and R is also false.

Q16: Assertion (A): Total flux through a closed surface is zero if no charge is enclosed by the surface. Reason (R): Gauss law is true for any closed surface, no matter what its shape or size is.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false and R is also false.

Q17: Assertion (A): If a proton and an electron are placed in the same uniform electric field, they experience different acceleration.
Reason (R): Electric force on a test charge is independent of its mass.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is NOT the correct explanation of A.
A is true but R is false.
A is false and R is also false.

Q18: The Electric flux through the surface (enclosing the same point charge $q$)

in Fig. (iv) is the largest.
in Fig. (ii) is the least.
in Fig. (ii) is same as Fig. (iii) but is smaller than Fig. (iv)
is the same for all the figures.

Q19: A hemisphere is uniformly charged positively. The electric field at a point on a diameter away from the centre is directed

perpendicular to the diameter
parallel to the diameter
at an angle tilted towards the diameter
at an angle tilted away from the diameter

Q20: An electric dipole placed in a non-uniform electric field can experience

a force but not a torque.
a torque but not a force.
always a force and a torque.
neither a force nor a torque.

Q21: Figure shows electric field lines in which an electric dipole $\vec{p}$ is placed as shown. Which of the following statements is correct?

the dipole will not experience any force.
the dipole will experience a force towards right.
the dipole will experience a force towards left.
the dipole will experience a force upwards.

Q22: A point charge $+q$, is placed at a distance $d$ from an isolated conducting plane. The field at a point $P$ on the other side of the plane is

directed perpendicular to the plane and away from the plane.
directed perpendicular to the plane but towards the plane.
directed radially away from the point charge.
directed radially towards the point charge.

Q23: If $\oint \vec{E} \cdot d\vec{S} = 0$ over a surface, then

the electric field inside the surface and on it is zero.
the electric field inside the surface is necessarily uniform.
the number of flux lines entering the surface must be equal to the number of flux lines leaving it.
all charges must necessarily be outside the surface.

Q24: The electric field inside a charged conductor is zero because:

Charges are tightly bound to the nuclei.
The electric field acts normally to the surface.
Charges reside on the surface of a conductor.
Electric field lines form closed loops.

Q25: When two different bodies are rubbed against each other, electrons are transferred from the material with:

higher work function to the material with lower work function.
lower work function to the material with higher work function.
higher mass to the material with lower mass.
higher permittivity to the material with lower permittivity.

Q26: In the process of charging by friction, if a glass rod is rubbed with silk cloth, the glass rod becomes positively charged because:

It gains protons from the silk cloth.
It gains electrons from the silk cloth.
It transfers protons to the silk cloth.
It transfers electrons to the silk cloth.

Q27: An electric dipole, when held at $30^\circ$ with respect to a uniform electric field of $10^4 \text{ N/C}$, experiences a torque of $9 \times 10^{-26} \text{ Nm}$. The magnitude of the dipole moment is:

$9 \times 10^{-30} \text{ C m}$
$1.8 \times 10^{-29} \text{ C m}$
$4.5 \times 10^{-30} \text{ C m}$
$1.8 \times 10^{-26} \text{ C m}$

Q28: What is the value of the proportionality constant $k$ in Coulomb's law $\left(F = k \frac{q_1 q_2}{r^2}\right)$ in free space?

$9 \times 10^9 \text{ Nm}^2\text{C}^{-2}$
$8.85 \times 10^{-12} \text{ C}^2\text{N}^{-1}\text{m}^{-2}$
$1.6 \times 10^{-19} \text{ C}$
$6.67 \times 10^{-11} \text{ Nm}^2\text{kg}^{-2}$

Q29: When an electric dipole is placed in a uniform electric field, the net force acting on it is:

$qE$
$2qE$
Zero
Dependent on angle $\theta$

Q30: The ratio of the magnitude of the electrostatic force to the gravitational force between an electron and a proton is approximately:

$10^{19}$
$10^{39}$
$10^{-39}$
$10^{42}$