Electric fields and charges practice · Medium

Two charges of $5\,\,\mu c$ and $- 45\,\,\mu c$ are separated by a distance of 42 cm. Electrostatic field strength from the smaller charge is zero at a distance of

Estimate the number of electrons in $100 \mathrm{~g}$ of water. How much is the total negative charge on these electrons?

A dipole has two charges $+1 \mu {C}$ and $-1 \mu C$ and each have mass $1 {~kg}$. The separation between the charges is $1 {~m}$. An electric field $20 \times 10^3 {v} / {m}$ is applied on the dipole. If the dipole is deflected through $2^{\circ}$ from the equilibrium position, time taken by it to come to the equilibrium position again is

Assertion:- Electrostatic energy does not follow superposition principle.
Reason:-Electrostatic energy density is a quadratic function.

Assertion:- When a positive point charge is placed near a neutral conductor then the Latter becomes negatively charged.
Reason:- Induction is possible in conductors only.

Assertion(A): If a bob of a simple pendulum is kept in a horizontal electric field, its period of oscillation will remain same.

Reason(R): If bob is charged and kept in horizontal electric field, then the time period will be decreased.

Assertion: Electric lines of force cross each other.

Reason: Electric field at a point superimposes to give one resultant electric field.

Two equal and opposite charges are placed at points $P$ and $Q.$ The null point on the line joining them is

An infinite line charge produces a field of $18 \times 10^4 \mathrm{~N} / \mathrm{C}$ at $0.02 \mathrm{~m}$. The linear charge density is

The bob of simple pendulum is hanging vertically down from a fixed identical bob by means of string of length $l$. If both bobs are charged with a charge with a charge $q$ each, time period of the pendulum is (ignore the radii of the bobs)

Gauss’s law of electrostatics would be invalid if

A force of $4N$ is acting between two charges in air if the space between them is completely filled with glass $\left( {{\varepsilon _r} = 8} \right)$, then the new force will be …… $N$

In a region, the intensity of an electric field is given by $E=8 \hat{i}+8 \hat{j}+\hat{k}$ in $\mathrm{NC}^{-1}.$ The electric flux through a surface $S=10 \hat{i} m^2$ in the region is

Electric charges under action of electric forces is called

A hollow metallic sphere of radius $10\;cm$ is given a charge of $3.2 \times {10^{ - 9}}$ $C$.The electric intensity at a point $4\;cm$ from the centre is

An electron is moving round the nucleus of a hydrogen atom in a circular orbit of radius $r.$ The coulomb force ${\vec F}$ between the two is 

The repulsive force between two equal charges $(Q)$ is $F.$ To reduce force by 25% how much charge is transferred from first to second:-

Two charges $+1 \mu \mathrm{C}$ and $+4 \mu \mathrm{C}$ are situated at a distance in air. The ratio of the forces acting on them is

Assertion:- Net charge density inside a conductor is zero.
Reason:- Equal and opposite charges are present in conductor.

Which of the following is the correct statement of Gauss law for electrostatics in a region of charge distribution in free space?

Two masses $M_1$ and $M_2$ carry positive charges $Q_1$ and $Q_2$, respectively. They are dropped to the floor in a laboratory setup from the same height where there is a constant electric field vertically upwards. $M_1$ hits the floor before $M_2$. Then,

Assertion: All the charges in a conductor get
distributed on whole of its outer surface.

Reason: In a dynamic system, charges try to
keep their potential energy minimum.

The surface charge density $\left( {\mathrm{in\;}C/{m^2}} \right)$ of the earth is about

If the electric field near the earth's surface be $300 \mathrm{~V} / \mathrm{m}$ directed downwards, then the surface density of charge on earth's surface is

A charge $Q$ is to be distributed on two conducting spheres. Find out values of charges on spheres so, that the repulsive force between them is maximum at fixed distance.

The force per unit charge is known as_____.

What is the magnitude of a point charge due to which the electric field 30cm away has the magnitude $2\;newton/coulomb$ $[1/4\pi {\varepsilon _0} = 9 \times {10^9}N{m^2}/{C^2}]$

Which of the following is false for electric lines
of force?

Assertion: The coulomb force is the dominating force in the universe.
Reason: The coulomb force is weaker than the gravitational force.

A charged bead is capable of sliding freely
through a string held vertically in tension. An
electric field is applied parallel to the string, so
that the bead stays at rest at middle of the
string. If the electric field is switched off
momentarily and switched on