Question

Direction: for the question 10 to 16 : Given paragraph in the following section describes a problem.
Apply your understanding of fundamental concepts and use the information in the paragraph to
answer the questions given at the end of the paragraph.
Coulomb's law enables us to calculate force of repulsion between two like charges or the force of
attraction between two unlike charges. We know that Coulomb's law, in a strict sense, applies to
stationary point charges. Magnitude of force between two static point charges is directly
proportional to product of magnitudes of the charges and it varies inversely with the square of the
separation between them. Besides, magnitude of force also depends on relative permittivity
(dielectric constant) of the medium. Consider two uncharged conducting spheres A and B of same
radius that has a small value. On charging, mass of A is found to reduce by 4.55 × 1017 kg and that
of B, is found to Increase. A and B are kept at such a separation r1 that if a third charge -32C is
placed 1m from A and along the line joining A and B, the entire system is in equilibrium. The third
charge is removed from the system; A and B are kept in contact and then placed at a separation ‘r2’ - Thus we have a system of point charges A and B placed a distance ‘r2’ apart. Force between^ and B
placed ‘r2’ apart has different values in different media, its maximum value being 32.4 N. When the
system is kept in a medium Y, it is; observed that magnitude of each charge has to be increased by
50% so that the force between them is 32.4 N. However, if the system is placed in a medium Y, it is
observed that magnitude of | each charge has to be increased by 50% and their separation-also need
to be reduced by 50% so that the force between them is still 32.4N.
Answer the following questions.
10. Charge on A before contact with B is
(a) +12C (b) +10C
(c) +8C (d) -6C
11. Charge on B before contact with A is
(a) -32C (b) -16 C
(c) +8C (d) +16 C
12. Separation r1 between A and B such that if a third charge -32C is placed lm from A, the
entire system will be in equilibrium, is
(a) 4 m (b) 3 m
(c) 2 m (d) 1 m
13. Charge on A after contact with B is
(a) -8C (b) -12C
(c) -16C (d) +8C
14. Separation r2 between A and B is
(a) 5 cm (b) 10 cm
(c) 20 cm (d) 40 cm
15. Dielectric constant of medium X is
(a) 4.5 (b) 2.25
(c) 6 (d) 8.25
16. When the system of A and B separated by r2 is kept in medium Y and magnitude of each
charge increased by 50% force between them remains 32.4N. What is the force between
them if neither the magnitude of any charge nor their separation is changed?
(a) 3.6 N (b) 12.5 N
(c) 16.2 N (d) 40 N

Answer 1

Answer:

charge of an object

Explanation:

(a) -8C (b) -12C

(c) -16C (d) +8C

14. Separation r2 between A and B is

(a) 5 cm (b) 10 cm

(c) 20 cm (d) 40 cm

15. Dielectric constant of medium X is

(a) 4.5 (b) 2.25

(