CBSE Important Questions

Electrostatics

Q. 1. The absolute permitivity of free space is 8.85 x 10^-12. What is the relative permitivity of free space and how ? (1)

Q. 2. Which among the following is a Scalar Quantity? (1)

1. Electric Dipole moment
2. Electric field Intensity due to a point charge
3. Electric Potential at the center of a uniformly charged sphere with Electric field intensity E
4. Electrostatic force acting on an oil drop

Q. 3. Two charges of 32 micro coulomb each, of opposite signs, are placed in a medium of absolute permitivity 9.8 x 10^-12 at a distance of 5cm apart. Does it form a dipole and If so what is the moment?. Calculate the force exist between them? (2)

Q. 4. State and prove Gauss’ theorem. (2)

Q. 5. Two hollow spheres of radii 10cm and 20cm are charged at a rate of 16 C per second. After charging for 5 seconds which sphere has more charge, higher charge density and how much? (3)

Q. 6. Derive an expression for the electric field intensity at any point on the equatorial line of a dipole. (2)

Q. 7. Two thin metal plates, A and B, of unit charge densities, are arranged in free space as shown. Find the magnitude of the electric files intensities at all the three regions and mark their direction. (2)

Q. 8. Explain how a metal rod can be positively charged by method of induction. (2)

Q. 9. Unit positive charges are placed at each corner of a regular polygon as shown. What is the electric field intensity at point O in the given figure? Justify. (2)

If a unit charge is placed at point o, what is the total electrostatics force experienced by this charge. (1)

Q. 10. Explain Attractive, Quantization and Superposition properties of charges. (3)

Q. 11. When two materials, A and B, are rubbed each other A became positively charged and B became negatively charged. If the charge on A is + 32 C, (3)

1. What is the charge on B?
2. Which material has more number of electrons and how much?
3. Which material has more mass?

Q. 12. An dipole is formed using + 10 C each, 6cm apart and placed in a uniform electric field of 3 N/C at an angle 30⁰ with respect to the field. What is the work needs to be done to move the dipole from 30⁰ to 60⁰. (2)

Q. 13. A cylinder is uniformly charged with a density of 0.2 cm^-2 on its curved outer surface, as shown. What is the total electric flux of the Gaussian surface of the cylinder? (3)

Q. 14. State Coulomb's law and explain it in vector form between two positive charges of q1 and q2. (4)

Q. 15. Draw diagrams to represent electric lines of force around point (+ve and –ve) charges, two unlike charges and two like charges. (2)