CBSE Class 12 Physics Chapter-2 Important Questions – Free PDF Download
Free PDF download of Important Questions with Answers for CBSE Class 12 Physics Chapter 2 – Electrostatic Potential and Capacitance 2 Marks Questions prepared by expert Physics teachers from latest edition of CBSE(NCERT) books only by CoolGyan to score more marks in CBSE board examination.
CBSE Class 12 Physics Chapter-2 Important Questions
CBSE Class 12 Physics Important Questions Chapter 2 – Electrostatic Potential and Capacitance
2 Marks Questions
1. Show mathematically that the potential at a point on the equatorial line of an electric dipole is Zero?
Ans. Electric potential at point P doe to the dipole
V = 
V=o
2. A parallel plate capacitor with air between the plates has a capacitance of
. What will be the capacitance if the distance between the plates is reduced by half and the space between them is filled with a substance of dielectric constant 6?
Ans. For air Co = 
Co =
Now d’ = d/2 and K = 6
3. Draw one equipotential surfaces (1) Due to uniform electric field (2) For a point charge (q < o)?
Ans.
4. If the amount of electric flux entering and leaving a closed surface are 
and 
respectively. What is the electric charge inside the surface?
Ans. Net flux = –
Since 
Q = 
5. A steam of electrons travelling with speed 
at right angles to a uniform electric field E is deflected in a circular path of radius r. Prove that 
?
Ans. The path of the electron traveling with velocity at right angles of 
is circular.
It requires a centripetal force 
which is provided by an electrostatic force f = eE
b
6. The distance between the plates of a parallel plate capacitor is d. A metal plate of thickness 
is placed between the plates. What will be the effect on the capacitance?
Ans. For air 
Thickness t = 
only when 
, Hence capacitance will get doubled.
7. Two charges 
are placed at points A and B 6 cm apart.
1. Identify an equipotential surface of the system.
2. What is the direction of the electric field at every point on this surface?
Ans. The situation is represented in the given figure.
An equipotential surface is the plane on which total potential is zero everywhere. This plane is normal to line AB. The plane is located at the mid-point of line AB because the magnitude of charges is the same.
1. The direction of the electric field at every point on this surface is normal to the plane in the direction of AB.
8. In a Van de Graaff type generator a spherical metal shell is to be a 
electrode. The dielectric strength of the gas surrounding the electrode is
. What is the minimum radius of the spherical shell required? (You will learn from this exercise why one cannot build an electrostatic generator using a very small shell which requires a small charge to acquire a high potential.)
Ans. Potential difference, V =
Dielectric strength of the surrounding gas = 
Electric field intensity, E = Dielectric strength =
Minimum radius of the spherical shell required for the purpose is given by,
Hence, the minimum radius of the spherical shell required is 30 cm.
9. A small sphere of radius 
and charge 
is enclosed by a spherical shell of radius
and charge
. Show that if is positive, charge will necessarily flow from the sphere to the shell (when the two are connected by a wire) no matter what the charge on the shell is.
Ans. According to Gauss’s law, the electric field between a sphere and a shell is determined by the charge on a small sphere. Hence, the potential difference, V, between the sphere and the shell is independent of charge . For positive charge , potential difference V is always positive.
10. Describe schematically the equipotential surfaces corresponding to
1. a constant electric field in the z-direction,
2. a field that uniformly increases in magnitude but remains in a constant (say, z) direction,
3. a single positive charge at the origin, and
4. a uniform grid consisting of long equally spaced parallel charged wires in a plane.
Ans. 1. Equidistant planes parallel to the x-y plane are the equipotential surfaces.
2. Planes parallel to the x-y plane are the equipotential surfaces with the exception that when the planes get closer, the field increases.
3. Concentric spheres centered at the origin are equipotential surfaces.
4. A periodically varying shape near the given grid is the equipotential surface. This shape gradually reaches the shape of planes parallel to the grid at a larger distance.