List of top Physics Questions on Electric Charges and Coulomb's Law asked in CBSE CLASS XII

Two small identical metallic balls having charges \(q\) and \(-2q\) are kept far apart at a separation \(r\). They are brought in contact and then separated at a distance \(\frac{r}{2}\). Compared to the initial force \(F\), they will now:

Two infinitely long straight wires having linear charge densities \(-\lambda\) and \(3\lambda\) are held vertically parallel to each other, distance \(r\) apart in free space. Find the nature and magnitude of the force/length exerted by one wire on the other.

Two small identical metallic balls having charges \(q\) and \(-2q\) are kept far apart at a separation \(r\). They are brought in contact and then separated at a distance \(\frac{r}{2}\). Compared to the initial force \(F\), they will now:

Two infinitely long straight wires having linear charge densities \(-\lambda\) and \(3\lambda\) are held vertically parallel to each other, distance \(r\) apart in free space. Find the nature and magnitude of the force/length exerted by one wire on the other.

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

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 \(17.0 × 10^{−22} Cm^{-2}\). What is E:
(a) in the outer region of the first plate,
(b) in the outer region of the second plate, and (c) between the plates?

An infinite line charge produces a field of \( 9 × 10^4 NC^{-1} \)at a distance of 2 cm. Calculate the linear charge density.

A point charge of \(2.0\,µC\) is at the centre of a cubic Gaussian surface 9.0 cm on edge. What is the net electric flux through the surface?

A uniformly charged conducting sphere of \( 2.4\,m\) diameter has a surface charge density of \(80.0\,µCm^{-2}\) .
(a) Find the charge on the sphere.
(b) What is the total electric flux leaving the surface of the sphere?

A point charge causes an electric flux of \(−1.0 × 10^3 Nm^2 C^{-1}\) to pass through a spherical Gaussian surface of 10.0 cm radius centered on the charge.
(a) If the radius of the Gaussian surface were doubled, how much flux would pass through the surface?
(b) What is the value of the point charge?

A point charge \(+10 µC\) is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.34. 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.)