CBSE Guess > Papers > Important Questions > Class XII > 2007 > Physics > Physics (Electrostatics) By: Mr. Abhishek Gupta

Electrostatics

Q. 1. What is the dielectric constant of Silver?

Q. 2. Find the work done in placing a charge of 8nC on a condenser of capacity 100micro-farad.

Q. 3. Find the electric field b/w 2 metal plates 5mm apart, connected by a 12V battery.

Q. 4. Write the value of Coulomb constant ( K ) and mention its units.

Q. 5. How many protons will have the total charge of 1C

Q. 6. The electrostatic force on a small sphere of charge 4C due to another small sphere of charge –8C in air is F. What is the distance b/w the 2 spheres. What is the force on the –8C sphere due to the first sphere. What will this force be if the 2 spheres are dipped in a liquid having dielectric constant K ?

Q. 7. An electron is placed inside a capacitor ( 5μf ). It is found to be stationary i.e. its weight is balanced by the electrostatic force. Find the potential difference across the plates of the capacitor if the plate area is A.

Q. 8. Equal charges each of 1C are placed at x = 0, 2 , 4 , 8 , 16 cm. Find the force experienced by the charge at x=2 cm. Define electric field intensity at x=2 and find it.

Q. 9. What is the work done in moving a charge 100nC from point A to point B 5cms apart, where both points A and B lie on the same equipotential surface? Explain your answer.

Q. 10. Define electric potential. What is line integral of electric field over a closed loop?

Q. 11. Define equipotential surface and draw EPS for a single point charge.

Q. 12. Define electric flux. Is it a vector quantity. Give its units. If the flux entering and leaving a closed surface is Φ1 and Φ2 find the charge inside that surface.

Q. 13. A uniform electric field E exists b/w the 2 charged plates as shown in the figure. What would be the work done in moving a charge q along the path A B ABCDA. Hence define conservative fields and give 2 properties.

Q. 14. Write 3 differences b/w charge and mass.

Q.15. Calculate the potential at the center of a square of side 1.414m, which carries at its 4 corner charges of 2nC , 1nC , -2nC , -3nC respectively. Also find E at the center.

Q. 16. Two point charges 4q and q are fixed a distance 2m apart. Find the point on the line joining them at which the net electric field intensity in zero. What is the potential at this point. If a charge of magnitude –3q is placed at this point, in which direction will it move. What will be its potential energy at this point?

Q. 17. When 2 capacitors C1 and C2 are connected in series the net is 1.2 farad, when connected in parallel the net capacitance is 5 farad. Find C1 and C2.

Q. 18. Charges of 4μC each are placed at the four corners of a square of side 1m. Find the electric field and potential at the center. Q1 What would these quantities be if one of the given charges were negative? 4m

Q. 19. Three charges –Q₁, +Q₂, -Q₃ are placed as shown in the 3m figure. Find in vector form the force acting on Q₂ charge.

Q. 20. Can a positively charged object attract a neutral object? Explain briefly

Q. 21. Find the equivalent capacitance b/w points A and B. Each capacitor is of 1μfarad B

Q. 22. A hollow sphere of radius R is given a charge Q. On a graph plot the variation of Electric field intensity versus distance from center. On another graph plot the potential against distance.

Q. 23. A certain region of space is to be protected from external electric field. Suggest 2 methods

Q. 24. Two point electric charges A and B of unknown magnitude and sign are placed d distance apart. The electric field is zero at a point, not b/w the charges but on the line joining them and closer to A. Write 2 essential conditions for this to happen

Q. 25. What are electric field lines. Give 4 properties and define neutral point.

Q. 26. Define capacitance and give its units. Explain the principle of a parallel plate capacitor and the use of earthing. Derive the formula for capacitance of a parallel plate capacitor.

Q. 27. State Gauss’s theorem. Give its mathematical expression. Derive an expression for the electric field intensity at any point due to an infinite plane sheet of charge of density σ C/m2