Electric Charges and Fields Set-1

Question 1

.  Two point charges placed in a medium of dielectric constant 5 are at a distance $r$ between them, experience an electrostatic force 'F'. The electrostatic force between them in vacuum at the same distance $r$ will be:

Accepted Answer

$5F$

Answer

$F$

Answer

$F/2$

Answer

$F/5$

Question 2

In an experiment three microscopic latex spheres are sprayed into a chamber and became charged with charges $+3e$, $+5e$ and $-3e$ respectively. All the three spheres came in contact simultaneously for a moment and got separated. Which one of the following are possible values for the final charge on the spheres?

Accepted Answer

$+6e$, $+6e$, $-7e$

Answer

$+5e$, $-1e$, $+5e$

Answer

$-4e$, $+3.5e$, $+5.5e$

Answer

$+5e$, $-8e$, $+7e$

Question 3

Two point charges $+8q$ and $-2q$ are located at $x=0$ and $x=L$ respectively. The point on $x$-axis at which net electric field is zero due to these charges is:

Accepted Answer

$2L$

Answer

$8L$

Answer

$4L$

Answer

$L$

Question 4

The electric potential $V$ at any point $(x, y, z)$ is given by $V = 3x^2$ where $x$ is in metres and $V$ in volts. The electric field at the point $(1	ext{m}, 0.2	ext{m})$ is:

Accepted Answer

$6 	ext{ V/m}$ along $(-	ext{x})$-axis

Answer

$6 	ext{ V/m}$ along $(+	ext{x})$-axis

Answer

$1.5 	ext{ V/m}$ along $(-	ext{x})$-axis

Answer

$1.5 	ext{ V/m}$ along $(+	ext{x})$-axis

Question 5

Assertion (A): On going away from a point charge or a small electric dipole, electric field decreases at the same rate in both the cases. 
Reason (R): Electric field is inversely proportional to square of distance from the charge or an electric dipole.

Accepted Answer

A is false and R is also false.

Answer

Both A and R are true and R is the correct explanation of A.

Answer

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

Answer

A is true but R is false.

Question 6

The electric field at $r = R$ (for a non-uniformly distributed nuclear charge $Z e$ within nucleus radius $R$) is:

Accepted Answer

independent of $a$

Answer

directly proportional to $a$

Answer

directly proportional to $a^2$

Answer

inversely proportional to $a$

Question 7

The electric field within the nucleus is generally observed to be linearly dependent on $r$. This implies:

Accepted Answer

$a = R$

Answer

$a = 0$

Answer

$a = R/2$

Answer

$a = 2R/3$

Question 8

Electric field intensity at point $P$ due to charge distributed over a sphere is:

Accepted Answer

$E = \frac{\sigma R^2}{\epsilon_0 2r^2}$

Answer

$E = \frac{1}{4\pi \epsilon_0} \frac{q}{r^2}$

Answer

$E = \frac{1}{4\pi \epsilon_0} \frac{2q}{r^2}$

Answer

$E = 0$

Question 9

When point $P$ is inside a conducting spherical shell:

Accepted Answer

$E = 0$

Answer

$E = \frac{1}{4\pi \epsilon_0} \frac{q}{r^2}$

Answer

cannot be calculated

Answer

remains constant everywhere inside the sphere (always non-zero)

Question 10

Which statement is true for Gauss's law:

Accepted Answer

The electric field over the Gaussian surface remains continuous and uniform at every point.

Answer

All the charges whether inside or outside the gaussian surface contribute to the electric flux.

Answer

Electric flux depends upon the geometry of the gaussian surface.

Answer

Gauss's theorem can be applied to non-uniform electric field.

Question 11

Assertion (A): A metallic shield in form of a hollow shell may be built to block an electric field. 
Reason (R): In a hollow spherical shield, the electric field inside it is zero at every point.

Accepted Answer

Both A and R are true and R is the correct explanation of A.

Answer

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

Answer

A is true but R is false.

Answer

A is false and R is also false.

Question 12

A charge 'q' is placed at the center of a cube of side 'l'. What is the electric flux passing through each face of the cube?

Accepted Answer

$q / (6 \epsilon_0)$

Answer

$q / \epsilon_0$

Answer

$q / (4 \epsilon_0)$

Answer

$0$

Question 13

A thin metallic spherical shell of radius $R$ carries charge $Q$. A point charge $Q/2$ is placed at its centre $C$. What is the magnitude of the force on the charge $Q/2$ at the centre?

Accepted Answer

Zero

Answer

$3Q^2 / (8\pi\epsilon_0 R^2)$

Answer

$Q^2 / (4\pi\epsilon_0 R^2)$

Answer

$Q / (4\pi\epsilon_0 R^2)$

Question 14

A thin metallic spherical shell of radius $R$ carries charge $Q$. A point charge $+2Q$ is placed outside the shell at point $A$ at a distance $x$ ($x > R$) from the centre $C$. Assuming the internal charge is $Q/2$ at $C$, the force exerted by the shell and internal charge on the charge $+2Q$ at point $A$ is:

Accepted Answer

$3Q^2 / (8\pi\epsilon_0 x^2)$

Answer

$Q^2 / (4\pi\epsilon_0 x^2)$

Answer

$3Q^2 / (4\pi\epsilon_0 x^2)$

Answer

Zero

Question 15

Figure shows six charged lumps of plastic coin. The cross-section of a Gaussian surface $S$ is indicated. What is the net electric flux through the surface?

Accepted Answer

$(q_1 - q_2 + q_3 - q_6) / \epsilon_0$

Answer

$(q_1 - q_2 - q_3 - q_6) / \epsilon_0$

Answer

$(q_1 - q_2 + q_3) / \epsilon_0$

Answer

$(q_1 - q_2 + q_3 - q_6 + q_4 + q_5) / \epsilon_0$

Question 16

If the sizes of charged bodies are very small compared to the distances between them, we treat them as ____________.

Accepted Answer

Point charges

Answer

Zero charges

Answer

Single charge

Answer

No charges

Question 17

The force per unit charge is known as ____________.

Accepted Answer

Electric field

Answer

Electric current

Answer

Electric potential

Answer

Electric space

Question 18

State true or false: The total charge of the isolated system is NOT conserved.

Accepted Answer

False

Answer

True

Answer

Cannot determine

Answer

Depends on velocity

Question 19

What is the dielectric constant of a metal?

Accepted Answer

Infinite

Answer

$-1$

Answer

$0$

Answer

$1$

Question 20

If the charge of $1 	ext{ C}$ is placed at a distance of $1 	ext{ m}$ from another charge of the same magnitude in a vacuum, it experiences an electrical force repulsion of magnitude ____________.

Accepted Answer

$9 	imes 10^{9} 	ext{ N}$

Answer

$9 	imes 10^{-9} 	ext{ N}$

Answer

$10 	imes 10^{9} 	ext{ N}$

Answer

$10 	imes 10^{-9} 	ext{ N}$

Question 21

The quantisation of charge indicates that

Accepted Answer

Charge, which is a fraction of charge on an electron, is not possible

Answer

A charge cannot be destroyed

Answer

Charge exists on particles

Answer

There exists a minimum permissible charge on a particle

Question 22

The property which differentiates two kinds of charges is called ____________.

Accepted Answer

Polarity of charge

Answer

Equality of charge

Answer

Fraction of charge

Answer

None of the option

Question 23

————— gives the information on field strength, direction, and nature of the charge.

Accepted Answer

Electric field

Answer

Electric current

Answer

Electric flux

Answer

Electric potential

Question 24

$F = k \cdot (q_1 \cdot q_2) / r^2$. This is given by which law?

Accepted Answer

Coulomb’s law

Answer

Faraday’s law

Answer

Newton’s law

Answer

Fleming’s law

Question 25

From where did the term electricity get its origin?

Accepted Answer

Greek name *elektron*

Answer

Latin word *virtum*

Answer

Scientist Charles Du Fay

Answer

Scientist William Gilbert

Question 26

Two charges are at distance $d$ apart in air. Coulomb force between them is $F$. If a dielectric material of dielectric constant $K$ is placed between them, the Coulomb force now becomes

Accepted Answer

$F/K$

Answer

$FK$

Answer

$F/K^2$

Answer

$K/F$

Question 27

A negatively charged object $X$ is repelled by another charged object $Y$. However an object $Z$ is attracted to object $Y$. Which of the following is the most possibility for the object $Z$?

Accepted Answer

neutral or negatively charged

Answer

positively charged only

Answer

negatively charged only

Answer

neutral or positively charged

Question 28

The magnitude of electrostatic force between two large conducting spheres carrying charges $Q_1$ and $Q_2$ are kept with their centres $r$ distance apart is not exactly $\frac{1}{4\pi\epsilon_0} \frac{Q_1 Q_2}{r^2}$ because

Accepted Answer

charges will shift towards the portions of the spheres which are closer and facing towards each other.

Answer

these are not point charges.

Answer

charge distribution on the spheres is not uniform.

Answer

charges on spheres will shift towards the centres of their respective spheres.

Question 29

The magnitude of electric field due to a point charge $2q$, at distance $r$ is $E$. Then the magnitude of electric field due to a uniformly charged thin spherical shell of radius $R$ with total charge $q$ at a distance $r/2$ ($r \gg R$) will be

Accepted Answer

$0$

Answer

$E/4$

Answer

$2E$

Answer

$4E$

Question 30

Consider an uncharged conducting sphere. A positive point charge is placed outside the sphere. The net charge on the sphere is then,

Accepted Answer

zero

Answer

negative and uniformly distributed over the surface of sphere

Answer

positive and uniformly distributed over the surface of sphere

Answer

negative and appears at a point on the surface of sphere closest to point charge

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