QUESTIONS
Q1. What is the work done in moving a test charge ‘q’ through a distance of 1 cm along the equatorial axis of an electric dipole? [1]
Hint : on equatorial line V=0
Q2. Why in Millikan’s Oil Drop experiment, the charge measured was always found to be of some discrete value and not any arbitrary value? [1]
Ans: Because charge is always quantized ie., Q = n x e
Q3. What is meant by electrostatic shielding? [1]
Ans.: Electric filed inside a cavity is zero.
Q4. Why an electric dipole placed in a uniform electric field does not undergoes acceleration? [1]
Ans: Because the net force on the dipole is zero (Fnet = 0).
Q5. Why electric field lines
(i) Can never intersect one another?
(ii) Cannot for closed loops sometimes?
(iii) Cannot have break in between? [1]
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
Q6. Show that at a point where the electric field intensity is zero, electric potential need not be zero. [2]
Ans: If E = 0; V= constant (since, E = – dV/dr)
Q7. What is the electric flux through the surface S in Vaccum? [2]
Ans.: q/ε0
Q8. Write the expression for the electric field, charge density for a uniformly charged thin spherical shell.
Â
Ans.: E = kQ/r^2 ; σ = Q/4πr^2
Q9.
Write the expression for the electric field in the regions I, II, III shown in the above figure.
Ans: E(I) =E(III) = 0 ; E(II) = σ/ε0
Q10. Two free protons are separated by a distance of 1 A0. if they are released, what is the kinetic energy of each proton when at infinite separation.  [2]
Hint : at inifinte distance, K.E. = e2/4πε0r
Q11. How does the electric flux, electric field enclosing a given charge vary when the area enclosed by the charge is doubled?   [2]
Ans: (a) Φ = constant (b) E is halved
