CBSE Class 12 Physics Current Electricity Notes Set B

Questions Marks

1. How does the force between the two charges vary when

(a) The system is immersed in a medium.

(b) When the distance between them is halved?

Ans : (a)F=1/K times F0 (b)F=4 times F0

2. How does the electric flux, electric field enclosing a given charge vary when the area enclosed by the charge is doubled?

Ans: (a) (b) E is halved

3. Why in Millikan’s Oil Drop experiment, the charge measured was always found to be of some discrete value and not any arbitrary value?

Ans: Because charge is always quantized ie., Q = n x e

4. Two electric lines never cross each other. Why? 

Ans: Two directions of electric filed at the point of intersection which is not possible.

5. What is meant by electrostatic shielding? 

Ans: Electric filed inside a cavity is zero.

6. Why an electric dipole placed in a uniform electric field does not undergoes acceleration? 

Ans: Because the net force on the dipole is zero. Fnet = 0 as F=

7. Why electric field lines

(i) Can never intersect one another?

(ii) Cannot for closed loops sometimes?

(iii) Cannot have break in between?

Ans : Because

(i) Electric field has an unique direction at any given point

(ii) Monopoles or single isolated charges exist unlike magnetism

(iii) Start from +ve charges and terminate at –ve charges.

ELECTRIC POTENTIAL

QUESTIONS

1 Is it possible that the potential at a point is zero, while there is finite electric field intensity at that point? Give an example.

Ans: Yes , Centre of a dipole

2.Is it possible that the electric field at a point is zero, while there is a finite electric potential at that point. Give an example.

Ans: Yes, Inside charged shell

3 Can two equipotential surfaces intersect? Justify your answer.

Ans: No. Otherwise it would mean two directions for force at a point.

4 Is potential gradient a vector or a scalar quantity?

Ans: Scalar quantity

5 Write the dimensional formula of ‘є0 ‘the permittivity of free space.

Ans: [M-1L-3T4A2]

6 An electric dipole is placed in an electric field due to a point charge. Will there be a force and torque on the dipole?

Ans: Yes, Both force and torque will act 2a

7 An electron is placed at A, in the presence of a point charge +q located at C, is moved to a point B, such that ABC an equilateral triangle. Find the work done in this process

Ans: Zero

8. Draw the graph showing the variation of electric potential with distance from the centre of a uniformly charged shell.

Ans 

9. Find the ratio of the electric field lines starting from a proton kept first in vacuum and then in a medium of dielectric constant 6.

Ans: 6 : 1

Please refer to attached file for CBSE Class 12 Physics Current Electricity.