Physics Electrostatics Class 12 Cbse Important questions last 5years questions and answer chapter 1
2. Does the charge given to a metallic sphere depend on whether it is hollow or solid?
3. Draw the pattern of electric fields lines , when a point charge -Q is kept near an uncharged conducting plate ?
4. what is electric flux through a cube of one side which enclosed an electric dipole ?
5. Two metallic spheres A and B kept on insutating stands are in contact with each other . A positively charged rod p is brought near the sphere A as show in figure . the two spheres are seperated from each other , and the rod p is removed . what will be nature of charges on spheres A and B ?
6. two charges of magnitudes -2q and +q are located at points (a,0) and (4a,0 ) respectively . what is electric flux due to charges when we take a sphere of radius 3a at the origin ?
7. A metal sphere is kept on an insulating stand . A negatively charged rod is brought near it , then the spheres is earthed . on removing the earthing and taking the negatively charged rod aways what will be the nature of charge on the sphere ?
8.Define electric dipole moment .
9.Describe the stable and unstable condition when dipole is placed in uniform electric field .
10. An electric dipole is held in a uniform electric field then find the torque and also find the stable and unstable condition ?
11. define electric flux and its units ?
12. what is gauss law in electrostatics and is true for any closed loop , no matter what is shape or size ?
13.Two identical point charges Q are kept 2m apart in air . A third charge q of unknow magnitude and sign is placed on the line joining the charges such the system remains in equilibrium . find the position and nature of q .
12. Five point charges , each of charges +q are placed on five vertices of a regular hexagon of side a find the magnitude of the resultant force on a charge -q placed at the centre of the hexagon .
13. represent graphically the variation of electric field with distance for a uniformly charged plane sheet ?
14. Two isolated metal spheres A and B have radii R and 2R respectively , and same charge q . find which of the two spheres have grater energy density just outside the surface of the spheres ?
15. four point charges Q,q,Q and q are placed at the corners of a square of side q . find the resultant force a charge Q .
16.Three point charges q, -4q, and 2q are placed at the vertices of an equilateral tringle of side l . obtain the magnitude of resultant force on q charge .
17. a simple pendulum consists of a small spheres of mass m suspended by a string of length l . the sphere carries a positive charge q . the pendulum is placed in a uniform electric field of strength E directed toward down . find the period of oscillation of the pendulum due to electrostatics forces on spheres , gravitational effect is ignore ?
18. A thin metallic spherical shell of radius R carries a charge Q on its surface . A point charge Q/2 is placed at the center c and another charge +2Q is placed outside the shell at A a distance x from the centre find the following
A) find the electric flux through the shell
B) State the law used
C) find the force onthe charges at centre c of the shell and at the point A also ?
19. three point elctric charges +q each are kept at the vertices of an equilateral tringle of side a . determine the magnitude and sign of the charge to be kept at the centroid of the tringle so that the charges at the vertices remains in equilibrium .
20. an infinitely long positively charged straight wire have linear charge density lemda . an electron is revolving around the wire as its centre with a constant velocity in a circular plane perpendicular to the wire . deduce the expression for its kinetics energy .
also plot the graph kinetic energy verses lemda .
21. Two small identical electrical dipoles AB and CD each of dipole moment p are kept at an angle of 120 . What is the resultant dipole moment of this combination ? if this system is subjected to electric field E directed along +x direction , what will be the magnitude and direction of the torque acting on this .
22. A right circular cylinder of lenth a and radius r has its center at the origin and its axis along the x axis so that one face is at x= +a/2 and the other at x=- a/2 . A uniform electric field is acting parallel to the x axis such that E = e i for x> 0 and E= -e i for x<0 . find out the flux
A) through the flat faces B) through the curved surface of the cylinder . what is the net outward flux through the cylinder and the net charge inside the cylinder?
23. the outward electric flux due to chage +Q is independent of the shape and size of the surface which enclosed it. give two reasons to justified statement .
24. two identical circular loops 1 and 2 of radius R each have linear charge densities -lemda and +lemda respectively . the loops are placed coaxially of the net electric field at the centre of loop 1.
25.derive the expression for the work done in rotating a dipole from the some angle in a uniform electric field E .
26. find the expression for the force and torque on an electric dipole kept in uniform electric field .
27.find an expression for the electric field strength at a distant point situated
a) on the axis and
b) along the equatorial line of an electric dipole .
28. A charge is distributed uniformly over a ring of radius R . obtain an expression for the electric intensity E at a point on the axis of the rings .Hence show that for point at large distance from the rings . it behaves like a point charge .
29. using the gauss theorem show mathematically that for any point outside the shell , the electric field due to a uniformly charged spherical shell is same as he entire charge on the shell ,is concentrated .
b) why do you expect the electric field inside the shell to be zero according to this theorem .
30. state gauss theorem in electrostatics , apply this theorem to obtain the expression for the electric field at a point due to an infinitely long , thin ,uniformly charged straight wire of linear charge density lemda .
31. define electri flux and unit .
b) using gauss law prove that the electric field at a point due to uniformly charged infinite plane sheet is independent of the distance from it.
c) how is the field directed id the sheet is positively charged or negatively charged .
32. apply the gauss theorem to find the electric field near a charged conductor .
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