Class – X Subject – Science

1.
A metal surface has a positive charge of 10^{-9} C .How many electrons
would have been removed from the metaLsurface? Ans-
6.25 x 109

2.
A polythene piece is rubbed with wool and it has been found to acquire a
negative charge of 3 x 10^{-7}C. *(i) *How many electrons have
transferred from wool to polythene piece?

*(ii) *is
there a transfer of mass from wool to polythene ? If yes,
how?
[n= 1.875 x 10^{12 },
mass =^{ }1.706 x 10^{-18}kg]

3.
Estimate the number of electrons and protons in 200g of pure water. Also give
the total positive
charge.
[
no. e=6.692 × 10^{26 } ,Total positive charge = 1.07 × 10^{7
}]

4.
Work out the number of electron which must be removed from a conductor so that
it acquires a charge of 3.2μC.[2×10^{13 }]

5.
Calculate
the charge carried by 12.5 X 10^{18}
electrons.

6. How many electrons will have a total charge of one coulomb?

7. Can a body have a charge of 0-8 x 10^{-19
}coulomb? Justify your answer by comment.

8. A comb drawn through person's hair on
a dry day causes 10^{22} electrons to leave the person's hair and stick to the comb.
Calculate the charge carried by the comb.[charge on comb= -1.6 × 10^{3 }C]

9. A negatively charged rod attracts a suspended object. Can we conclude that the object is positively charged?

10. Two point charges q_{1} and q_{2} are
such that q_{1}q_{2}
> 0. What is the nature of force between the two charges?

11. Two point charges q_{x} and q_{2} are
such that q_{1}q_{2} < 0.
What is the nature of the force between the
two charges?

12. How is the mass of a body affected on charging?

13. What is the basic cause of quantisation of charge?

14. State the principle of quantisation of charge. What is the least value of electric charge available?

15. What is meant by conservation of charge?

16. Write S.I. unit of charge.

17. Two conductors A and *B *are joined by a
copper wire. State the direction of flow of electrons in each of the following cases: (i) If A is
positively charged and *B *is uncharged, (ii) If A is negatively charged and *B *is uncharged, (iii) If A is positively charged and *B *is
negatively charged.

18. How is the direction of flow of current between the two charged conductors determined by their potentials?

19. Explain the concept of electric potential difference in terms of work done in transferring the charge.

20. Define the term potential difference?

21. State and define the S.I. unit of potential difference.

22. The relationship between volt, joule and coulomb is : a. volt = joule x coulomb b. joule = coulomb x volt c. coulomb x joule x volt = 1 d. Joule = coulomb/volt

23. 'The potential difference between two conductors is 1 volt'. Explain the meaning of this statement.

24. What do you understand by the term resistance?

25. Explain why does a metal wire when connected to a cell offer resistance to the flow of current.

26. State the S.I. unit of resistance.

27. How are the potential difference *(V), *current (I)
and resistance *(R) *related?

28. 'The resistance of a wire is 1 ohm'. Explain the meaning of this statement.

29. How is the current flowing in a conductor changed if the resistance of conductor is doubled keeping the potential difference across it the same?

30. State *three *factors on which the resistance of a wire
depends. Explain how the resistance depends on the factors stated by you.

31. Distinguish between conductors and insulators. Give some of their examples.

32. How is the resistance of a wire affected if its (a) length is doubled, (b) radius is doubled ?

33. A bulb is connected to a cell. How is the resistance of circuit affected if another identical bulb is connected (i) in series, (ii) in parallel, with the first bulb?

34. Name the physical quantities of which the units are (i) volt, (ii) coulomb, (iii) ohm, (iv) ampere.

35. In transferring 1.5 C charges through a metallic wire, 9 J of work is needed. Find the potential difference across the wire.

36. A cell of potential difference 12 V is connected to a
bulb. The resistance of filament of the bulb when
it glows, is 24 *Ω*. Find the current drawn from the cell.

37. Show that one ampere is equivalent to a flow of 6.25 x 10^{18
}elementary charges.

38. 10^{20} electrons, each having a charge of 1.6 x 10^{19} C, pass from a point A towards another'
point B in 0.1s , What is the current in ampere ? What is its direction?

39. How many electrons pass through a lamp in one minute, if the current is 300 mill amperes?

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