  Previous Year Questions

## Electric Charges And Fields

- Practice Previous Year questions to get a better idea of the CBSE exam.
1
Derive an expression for the electric field E due to a dipole of length at a point distant r from the centre of the dipole on the axial line.
2
An infinitely large thin plane sheet has a uniform surface charge density . Obtain the expression for the amount of work done in bringing a point charge q from infinity to a point, distant r, in front of the charged plane sheet.
3
Fill in the blank with appropriate answer :
Electric flux through a spherical surface shown in the figure, is _______ .
4
(a) Define electric flux. Is it a scalar or a vector quantity?
A point charge is at a distance of directly above the centre of a square of side , as shown in the figure. Use Gauss' law to obtain the expression for the electric flux through the square.
(b) If the point charge is now moved to a distance from the centre of the square and the side of the square is doubled, explain how the electric flux will be affected.
5
Five point charges, each of value +q are placed on five vertices of a regular hexagon of side L. What is the magnitude of the force on a point charge of value -q placed at the centre of the hexagon?
6
Two metallic spheres and kept on insulating stands are in contact with each other. A positively charged rod is brought near the sphere as shown in the figure. The two spheres are separated from each other, and the rod is removed. What will be the nature of charges on spheres and ?
7
A metal sphere is kept on an insulating stand. A negatively charged rod is brought near it, then the sphere is earthed as shown. On removing the earthing, and taking the negatively charged rod away, what will be the nature of charge on the sphere? Give reason for your answer.
8
Explain briefly, using a paper diagram, the difference in behaviour of a conductor and a dielectric in the presence of external electric field.
9
A particle of charge and mass is moving with a velocity . At the particle enters in a region having an electric field (in . Find the velocity of the particle at .