Electric fields and charges practice · Medium

Two point charges $+ 3\mu C$ and $+ 8\mu C$ repel each other with a force of 40$N$. If a charge of $- 5\mu C$ is added to each of them, then the force between them will become

An electron moves a distance of $6 \mathrm{~cm}$ when accelerated from rest by an electric field of strength $2 \times 10^4 \mathrm{~NC}^{-1}$. Calculate the time of travel. The mass and charge of electron are $9 \times 10^{-31} \mathrm{~kg}$ and $1.6 \times 10^{-19} \mathrm{C}$ respectively.

Electric charge is uniformly distributed along a long straight wire of radius 1mm. The charge per cm length of the wire is ${\cal Q}$ coulomb. Another cylindrical surface of radius 50 cm and length 1m symmetrically encloses the wire. The total electric flux passing through the cylindrical surface is

Calculate the ratio of electric to gravitational force between two electrons.

A negatively charged oil drop is prevented from falling under gravity by applying a vertical electric field $100V\;{m^{ - 1}}.$ If the mass of the drop is $1.6 \times {10^{ - 3}}g,$ the number of electrons carried by the drop is $\left( {g = 10m{s^{ - 2}}} \right)$

Two charges of $50\,\mu c$ and $100\,\mu c$ are separated by a distance of $0.6\,m$. The intensity of electric field of a point midway between them is ….$\times {10^6}\frac{v}{m}$

Statement-1: Total work done by non-uniform electric field on a charged particle starting from rest till any time is non-negative. (assume no other forces act on the charged particle).
Statement-2: The angle between electrostatic force an velocity of the charged particle released from rest in non-uniform electric field is always acute. (assume no other forces act on the charged particle).

If the electrostatic force on a small sphere of charge $0.4 \mu \mathrm{C}$ due to another small sphere of charge $-0.8 \mu \mathrm{C}$ in air is $0.2 \mathrm{~N}.$ The separation of the spheres is $\left(\mathrm{k}=9 \times 10^9 \mathrm{~N} \mathrm{~m}^2 / \mathrm{C}^2\right)$

Assertion: Two charges ${q}_1$ and ${q}_2$ are placed at separation $r$. Then magnitude of force on each charge is $F$.

Reason: Now a third charge ${q}_3$ is placed near ${q}_1$ and ${q}_2$ Then force on ${q}_1$ due to ${q}_2$ remains ${F}$.

The electric field at a distance $\frac{{3R}}{2}$ from the centre of a charged conducting spherical shell of radius $R\;\mathrm{is}\;E$. The electric field at a distance $\frac{R}{2}$ from the centre of the sphere is

Select the correct statements from the following
(i) inside a charged or neutral conductor, electrostatic field is zero
(ii) the electrostatic field at the surface of the charged conductor must be tangential to the surface at any point
(iii) there is no net charge at any point inside the conductor

Two identical conducting balls $A$ and $B$ have positive charges ${q_1}$ and ${q_2}$ respectively but ${q_1} \ne {q_2}.$ The balls are brought together so that they touch each other and then kept in their original positions. The force between them is

A $10\,\mu C$ charge is divided into two equal parts and kept at 1 cm distance. Find repulsion between charges.

An electron is liberated from the lower of the two large parallel metal plates separated by a distance of $20 \mathrm{~mm}$. The upper plate has a potential of $+2400 \mathrm{~V}$ relative to the lower plate. How long does the electron take to reach the upper plate? Take $\frac{e}{m}$ of electrons $1.8 \times 10^{11} \mathrm{~C} \mathrm{~kg}^{-1}$.

Two charges of $50\,\mu c$ and $100\,\mu c$ are separated by a distance of $0.6\,m$. The intensity of electric field of a point midway between them is ….$\times {10^6}\frac{v}{m}$

The work done in placing a charge of $8 \times 10^{-18}$ coulomb on a condenser of capacity 100 micro-farad is

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

A spherical rubber balloon carries a charge, uniformly distributed over the surface. As the balloon is blown up and increases in size, the total electric flux coming out of the surface

Two conducting spheres of radii ${R_1}$ and ${R_2}$ having charges ${Q_1}$ and ${Q_2}$ respectively are connected to each other. There is

The force between two charged particle placed in air at separation $x$ is $F_0$. Both the charged particle immerged in a medium of dielectric constant $K$ without changing separation between two charge, then net force on one of the particle is now

One metallic sphere $A$ is given positive charge whereas another identical sphere $B$ of exactly same mass as of $A$ is given equal amount of negative charge. Then

The net electric flux associated with a closed surface which encloses $1 \mathrm{C}$ positive charge is equal to (In SI unit)

The point charges $Q$ and $- 2Q$ are placed at same distance apart. If the electric field at the location of $Q$ is $E$, find its value at the location of $- 2Q$ is

For coulomb force to be operative the least side of atom will be

At a point in space, the electric field points towards north. In the region surrounding this point, the rate of change of potential will be zero along

A force of 16 N is acting between two charges in air. If the space between them is completely filled with glass $\left( {{ \in _r} = 10} \right),$ then new force will be

The Electric field at a point is

The total electric flux through a cube when a charge $8q$ is placed at one corner of the cube is

In Van de Graaff generator, the process of spraying the charge is called:

Consider the following statements and select the incorrect statement.