List of top Physics Questions asked in CBSE CLASS XII

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 \(8.0 × 10^3 N m^2 C^{-1}. \)
(a) What is the net charge inside the box? 
(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?

Consider a uniform electric field \(E = 3 × 10^3 \,\hat{i} NC^{-1}\). 
(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? 
(b) What is the flux through the same square if the normal to its plane makes a \( 60^0\) angle with the x-axis?

A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is \(1.5 × 10^3 NC^{-1}\) and points radially inward, what is the net charge on the sphere?

What is the net flux of the uniform electric field of Exercise 1.15 through a cube of side 20 cm oriented so that its faces are parallel to the coordinate planes?

(a) Two insulated charged copper spheres A and B have their centers separated by a distance of 50 cm. What is the mutual force of electrostatic repulsion if the charge on each is \(6.5 × 10^{−7} C\)? The radii of A and B are negligible compared to the distance of separation. 
(b) What is the force of repulsion if each sphere is charged double the above amount, and the distance between them is halved?

A polythene piece rubbed with wool is found to have a negative charge of \(3 × 10^{−7} C\). 
(a) Estimate the number of electrons transferred (from which to which?) 
(b) Is there a transfer of mass from wool to polythene?

A system has two charge s \(q_A = 2.5 × 10^{−7} C\) and \(q_B = −2.5 × 10^{−7 }C\) located at points A: (0, 0, − 15 cm) and B: (0, 0, + 15 cm), respectively. What are the total charge and electric dipole moment of the system?

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.

The electrostatic force on a small sphere of charge 0.4 µC due to another small sphere of charge − 0.8 µC in air is 0.2 N.
(a) What is the distance between the two spheres?
(b) What is the force on the second sphere due to the first?