BHARTIYAM VIDYA NIKETAN
Subject- Physics
Date:
CLASS- XII
WORKSHEET No.1
1. 1 Stat-Coulomb = -------- Coulomb
(a) 3 × 109
(b) 3 × 10-9
(c)
× 109
(d) )
× 10-9
2. Which of the following is not an insulator?
(a) Glass
(b) Rubber
(c) Ebonite
(d) Human body
3. An object is charged when it has a charge imbalance, which means the
(a) Object contains no electrons
(b) Object contains no protons
(c) Object contains equal number of electrons and protons
(d) Object contains unequal number of electrons and protons
4. The cause of charging is
(a) Actual transfer of protons
(b) Actual transfer of electrons
(c) Actual transfer of neutrons
(d) None of the above
5. When a plastic comb is passed through dry hair, the charge acquired by the comb is
(a) Always negatives
(b) Always positive
(c) Sometimes negative
(d) None of the above
6. Out of glass (rod) and silk (Cloth), work function of glass is
(a) Smaller
(b) Larger
(c) Equal
(d) None of the above
7. The cause of quantization of electric charge is
(a) Transfer of Electrons
(b) Transfer of Protons
(c) Transfer of Integral number of electrons
(d) None of the Above
8. What is not true?
(a) It is not possible to create or destroy net charge carried by any isolated system
(b) Charges can be created or destroyed in equal unlike pairs only.
(c) Proper signs have to be used while adding the charges in a system
(d) Excess of electrons over protons in a body is responsible for positive charge of the body.
9. Charge on a body which carries 200 excess electrons is.
(a) – 3.2 × 10-18 C
(b) 3.2 × 10-18 C
10. The value of absolute electrical permittivity of free space is
(a) 9 × 109 Nm2 C-2
(b) 9 × 10-9 Nm2 C-2
(c) 8.85 × 10-12 C2 N-1 m-2
(d) 8.85 × 10-12 C2 Nm-2
(c) 3.2 × 10-17 C
(d) 3.2 × 10-17 C
BHARTIYAM VIDYA NIKETAN
Subject- Physics
Date:
CLASS- XII
WORKSHEET No.2
1. The electric charge of any body is actually a surplus or deficit of electrons. Why not protons?
2. Two free protons and two free electrons are separated by the same distance. Compare coulomb’s
forces of repulsion between the pair of protons and pair of electrons.
3. A charge Q is kept in the inner cavity and a charge 2 Q is given to the inner shell. A charge 3 Q is
given to the outermost shell, as shown in fig. 1(a).20. Find the charges at the surfaces A,B and C.
4. A negatively charged ebonite rod attracts a suspended ball of straw. Can we infer that the ball is
positively charged?
5. Can two similarly charged balls attract each other?
6. Two identical metallic spheres of exactly equal masses are taken. One is given positive charge of q
coulomb and other, an equal negative charge. Are their masses after charging equal?
7. A glass rod rubbed with silk is brought close to two uncharged metallic spheres in contact with each
other, inducing charges on them as shown in fig. 1 (a). 21 (a).
Describe what happens when
(i)
The spheres are slightly separated and
(ii)
The glass rod is subsequently removed and finally.
(iii)
The spheres are separated far apart.
8. A body A repels another body B, A attracts body C,C repels body D. It is given that body D is
positively charged. What is the charge on body B.
9. Explain why a neutral object can be attracted to a charged object. Why can this neutral object not be
repelled by a charged object?
10. When a hand approaches a charged weight suspended with a silk thread, the weight is attracted
towards the hand. Why does this occur?
11. (a) A comb run through one’s hair attracts small bits of paper. Why? What happens if the hair are
wet or if it is a rainy day?
(b) Ordinary rubbers is an insulator. But the special rubber tyres of aircrafts are made slightly
conducting. Why is this necessary?
(c) Vehicles carrying inflammable materials usually have metallic ropes touching the ground during
motion. Why?
(d) A bird perches on a bare high power line, and nothing happens to the bird. A man standing on the
ground touches the same line and gets a fatal shock. Why
12. How can you charge a metal sphere negatively without touching it?
13. An insulating rod carries some net charge, and a copper sphere is neutral. The rod and the sphere do
not touch. Can there be force of attraction / repulsion between the two?
14. Neutral metal objects, especially in industry, are often coated with electrically charged paint or powder
particles stick on the metal objects?
15. Figure 1 (a). 22 shows two protons (symbol P) and one electron (symbol e) on a straight line AB. What
is the direction of net electrostatic force on the central proton?
16. Give some points of dissimilarity and similarity between electrostatic forces and gravitational forces.
17. The electrostatic force between two charges is a central force. Why?
18. How is coulomb force between two charges affected by the presence of third charge.
19. If two objects repel one another, you know both carry either positive charge or negative charge. How
would you determine whether these charges are positive or negative?
20. Plot a graph showing the variation of coulomb force (F) versus
, where r is the distance between
two charges of each pair of charges:
(1
C, 2
C) and (2
C, - 3
C). Interpret the graphs obtained.
21. Is coulomb’s law in electrostatics valid in all situations?
22. What is the cause of charging?
23. An isolated conducting sphere is given a positive charge. Does its mass increase, decrease or remain the
same?
24. An ebonite rod is rubbed with fur or wool. What type of charges do they acquire?
…………………..