Two point charges $q_A = 3 \mu C$ and $q_B = -3 \mu C$ are located 20 cm apart in vacuum. (a) What is the electric field at the midpoint O of the line AB joining the two charges?

A point charge of $2.0 \mu C$ is at the centre of a cubic Gaussian surface 9.0 cm on edge. What is the net electric flux through the surface?

Two point charges $q_A = 3 \mu C$ and $q_B = -3 \mu C$ are located 20 cm apart in vacuum. (b) If a negative test charge of magnitude $1.5 \times 10^{-9}$ C is placed at this point, what is the force experienced by the test charge?

A uniformly charged conducting sphere of 2.4 m diameter has a surface charge density of $80.0 \mu C/m^2$. (a) Find the charge on the sphere.

Check that the ratio $\frac{ke^2}{G m_e m_p}$ is dimensionless. Look up a Table of Physical Constants and determine the value of this ratio. What does the ratio signify?

A uniformly charged conducting sphere of 2.4 m diameter has a surface charge density of $80.0 \mu C/m^2$. (b) What is the total electric flux leaving the surface of the sphere?

Careful measurement of the electric field at the surface of a black box indicates that the net outward flux through the surface of the box is $8.0 \times 10^3$ Nm$^2$/C. (a) What is the net charge inside the box?

A polythene piece rubbed with wool is found to have a negative charge of $3 \times 10^{-7}$ C. (a) Estimate the number of electrons transferred (from which to which?)

The electrostatic force on a small sphere of charge $0.4 \mu C$ due to another small sphere of charge $-0.8 \mu C$ in air is 0.2 N. (b) What is the force on the second sphere due to the first?

An infinite line charge produces a field of $9 \times 10^4$ N/C at a distance of 2 cm. Calculate the linear charge density.

What is the net flux of the uniform electric field of Exercise 1.14 through a cube of side 20 cm oriented so that its faces are parallel to the coordinate planes?

A polythene piece rubbed with wool is found to have a negative charge of $3 \times 10^{-7}$ C. (b) Is there a transfer of mass from wool to polythene?

Two insulated charged copper spheres A and B have their centres separated by a distance of 50 cm. What is the mutual force of electrostatic repulsion if the charge on each is $6.5 \times 10^{-7}$ C? The radii of A and B are negligible compared to the distance of separation.

Explain the meaning of the statement ‘electric charge of a body is quantised’.

A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is $1.5 \times 10^3$ N/C and points radially inward, what is the net charge on the sphere?

Two large, thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs and of magnitude $17.0 \times 10^{-22}$ C/m$^2$. What is $E$: (a) in the outer region of the first plate,

Figure 1.30 shows tracks of three charged particles in a uniform electrostatic field. Give the signs of the three charges. Which particle has the highest charge to mass ratio?

Two identical small conducting spheres, each of mass 0.1g, are suspended from the same point by two silk threads of length 0.5m. After giving each sphere an equal charge of 2µC ,the threads make an angle of 30° with each other in equilibrium.

Calculate:

1)The distance between the two spheres.

An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not?

Consider a uniform electric field $E = 3 \times 10^3 \hat{i}$ N/C. (a) What is the flux of this field through a square of 10 cm on a side whose plane is parallel to the yz plane?