A point charge ((+10 \mu C)) is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.31. What is the magnitude of the electric flux through the square? (Hint: Think of the square as one face of a cube with edge 10 cm.)

         

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

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,

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?

Consider a uniform electric field $E = 3 \times 10^3 \hat{i}$ N/C. (b) What is the flux through the same square if the normal to its plane makes a $60^{\circ}$ angle with the x-axis?

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?

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?

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?

Explain why two field lines never cross each other at any point?

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. What is the force on the second sphere due to the first?

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

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

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?

Explain why two field lines never cross each other at any point?

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

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?

A point charge causes an electric flux of $-1.0 \times 10^3$ Nm$^2$/C to pass through a spherical Gaussian surface of 10.0 cm radius centred on the charge. (a) If the radius of the Gaussian surface were doubled, how much flux would pass through the surface?

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. (a) What is the distance between the two spheres?

Why can one ignore quantisation of electric charge when dealing with macroscopic i.e., large scale charges?

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.