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.)

                      

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 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?

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?

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?

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 $80.0 \mu C/m^2$. (b) What is the total electric flux leaving the surface of the sphere?

What is the force of repulsion if each sphere is charged double the above amount, and the distance between them is halved?

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.

Four point charges $q_A = 2 \mu C$, $q_B = -5 \mu C$, $q_C = 2 \mu C$, and $q_D = -5 \mu C$ are located at the corners of a square ABCD of side 10 cm. What is the force on a charge of $1 \mu C$ placed at the centre of the square?

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. (b) If the net outward flux through the surface of the box were zero, could you conclude that there were no charges inside the box? Why or 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 $E$: (b) in the outer region of the second plate, and

What is the force between two small charged spheres having charges of $2 \times 10^{-7}$ C and $3 \times 10^{-7}$ C placed 30 cm apart in air?

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.

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

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?

When a glass rod is rubbed with a silk cloth, charges appear on both. A similar phenomenon is observed with many other pairs of bodies. Explain how this observation is consistent with the law of conservation of charge.

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?

An electric dipole with dipole moment $4 \times 10^{-9}$ C m is aligned at $30^{\circ}$ with the direction of a uniform electric field of magnitude $5 \times 10^4$ NC$^{-1}$. Calculate the magnitude of the torque acting on the dipole.