Summer Holiday Homework: Class 10 Science Physics
Very Short Answer Questions:
1. A battery is connected to a conductor. The
end A is connected to the positive terminal and the end B to the negative
terminal. What is the direction of the flow of electrons in the wire?
2. Define resistance of a conductor. What is
its SI unit?
3. Define the unit ohm!.
4. Distinguish between an open and a closed
electric circuit.
5. Explain the meaning of the statement
$potential difference between two points is 5 volt&
6. Give one example of a decomposition
reaction which is carried out with electricity.
7. Give one example of a thermal decomposition
reaction.
8. Give one example of an exothermic reaction
and one of an endothermic reaction.
9. Give one example of an oxidation-reduction
reaction which is also a combination reaction.
10. Give one example of an oxidation-reduction
reaction which is also a displacement reaction.
11. How does the heat produce by a current
passing through a fixed resistance wire depend on the magnitude of current I?
12. How many joules are equal to 1 watt hour?
13. How should the two resistances of 2 ohms
each be connected so as to produce an equivalent resistance of 1 ohm?
14. If the current passing through conductor
is doubled, what will be the change in heat produced?
15. In which type of combination is the
resultant resistance more than either of the individual resistances?
16. Keeping the potential difference constant
the resistance of a circuit is doubled. By how much does the current change?
17. Name the physical quantity whose unit is (
i ) kilowatt ( ii ) kilowatt hour
18. Name two devices that work on the heating
effect of electric current.
19. One coulomb of charge flows through any
cross-section of a conductor in one second. What is the current flowing through
the conductor?
20. State the law, which relates the current
in a conductor to the potential difference across its ends.
21. State the relation between potential difference,
work done and charge moved.
22. The current passing through room heater
has been halved. What will happen to the heat produced by it?
23. Two resistances A and B are connected by
turn : ( i ) in parallel , and ( ii ) in series . In which case the
resultant resistance will be less than either of the
individual resistances?
24. What are anti-oxidants? Why are they added
to fat and oil containing foods?
25. What happens to the resistance, as the
conductor is made thinner?
26. What is meant by the statement $the
resistivity of a conductor is one ohm metre&?
27. What is the condition under which electric
charge can flow through a conductor?
Short Answer
Questions:
28. What is the ratio of potential difference
and current know as?
29. What kind of plot would you expect when
current, I is plotted against potential, V ?
30. Which chemical reaction is involved in the
corrosion of iron?
31. Which effect of current is utilized in an
electric bulb?
32. Which effect of current is utilized in the
working of an electric fuse?
33. Which particles constitute the electric
current in a metallic conductor?
34. Which term is used to indicate the
development of unpleasant smell and taste in fat and oil containing foods due to
oxidation?
35. Write down a formula that states the
relation between potential difference current and resistance.
36. Write down the expression for the
resistance of a metallic wire in terms of the resistivity.
37. Write down the formula for heat produced
when current, I , is passed through a resistance R for time t.
Short Answer Questions:
38. A 100 watt electric bulb is lighted for 2
hours daily and four 40 watt bulbs are lighted for 4 hours every day.
Calculate the energy consumed (in kWh) in 30 days. ( Ans :
25.2kWh)
39. A bulb is rated at 200 V, and 100 W. What
is its resistance? Five such bulbs are lit for 4 hours. How much electrical
energy is consumed? Calculate the cost if the rate is 50 paise per unit.
40. A colourless lead salt, when heated,
produces a yellow residue and brown fumes.
(a) Name the brown fumes.
(b) Write a chemical equation of the reaction involved.
41. A copper wire has a diameter of 0.5 mm and
a resistivity of 1.6 ohm cm. How much of this wire would berequired to make a
10 ohm coil?
42. An electric bulb of resistance 480 W is
connected to 220 V mains. Find the amount of electrical energy consumed in 10 s
?
43. Calculate the equivalent resistance when
two resistances of 3 ohms and 6 ohms are connected in parallel.
44. Calculate the resistance of 1 metre of
copper wire that has a cross-sectional area of area of about 2 ´ 10@2 cm2. Compare the value of this resistance with
that to a flashlight bulb, which has a power rating of 1 W and operates at 3 V.
What does this comparison tell you? (Resistivity of copper = 1.62x 108
ohm m ) ( 3 ) Ans : 8.1 109 W
, 9W)
45. Distinguish between resistance and
resistivity.
46. Explain why, the current that makes the
heater element very hot, only slightly warms the connecting wires
leading to the heater.
Short Answer Questions:
47. Carbon monoxide reacts with hydrogen under
certain conditions to form methanol CH3 OH . Write a balanced
chemical equation for this reaction indicating the physical states of reactants
and product as well as the conditions under which this reaction takes place.
48. Define the following in terms of gain or
loss of hydrogen with one example each: (i) oxidation (ii) reduction
49. Explain why, food products containing fats
and oils are packaged in nitrogen.
50. Explain with example, how the physical
states of the reactants and products can be shown in a chemical equation.
51. Give an example of a Redox reaction,
naming the substances oxidized and reduced.
52. Derive a relation between SI unit and commercial unit of electrical energy.
53. The electric power consumed by a device may be calculated by using either of the two expressions
P=l 2R or P = V2/R
The first expression indicates that it is directly proportional to R whereas the second expression indicates inverse proportionality. How can the seemingly different dependence of P on R in these expressions be explained?
54. With the help of a diagram, deduce the equivalent resistance of three resistances connected in series.
55. With the help of a diagram, deduce the equivalent resistance of three resistances connected in parallel.
55. In the reaction represented by the
equation ( ) CuO s + H2 (g ) ®
Cu(s )+ H2O(l )
(a) Name the substance oxidised (b) Name the oxidising agent
56. One coulomb of charge flows through any
cross section of conductor in 1 second. What is the current flowing through it?
57. Potential difference between two points of
a wire carrying 2 A current is 0.1 V. Find the resistance between the points. 6 W
12 W 3 W
3W
58. State the characteristics of chemical
reactions.
59. State three factors on which the heat
produced by an electric current depends.
60. State whether an electric heater will
consume more electrical energy or less energy per second when the length of its heating element is reduced. Give
reasons for your answer.
61. What is a balanced chemical equation? Why
should chemical equations be balanced?
62. States Ohm’s law. How is it used to define
the unit of resistance?
Short Answer Questions:
63. Three resistances of 4 W, 5 W and 9 W are
connected in series. The potential difference across the combination is 36 V.
Calculate the potential difference across each resistor.
64. Two exactly similar heating resistances
are to be used connected across a mains supply to heat some water. Is more heat
obtained per minute if they are connected in series or if they are connected in
parallel? Justify.
65. Two resistances when connected in parallel
give resultant value of 4 ohm; when connected in series the value becomes 18
ohm. Calculate the value of each resistance.
66. What are the various ways in which a chemical
equation can be made more informative? Give examples to illustrate your answer.
67. What is a chemical equation? Explain with
the help of an example.
68. What is an electric circuit? Explain with
the help of a diagram.
69. What is meant by a chemical reaction? Give
one example of a chemical reaction.
70. What is the conventional direction of the
flow of electric current? How does it differ from the direction of flow of
electrons?
71. When particle carrying charge 10x 106
coulombs is brought from infinity to a point P, 2 x 103 joules of work
is done. What is the potential at the point P?
72. When copper powder is heated strongly in
air, it forms copper oxide. Write a balanced chemical equation for this
reaction. Name (i) substance oxidized, and (ii) substance reduced.
73. Why does the colour of copper sulphate
solution change when an iron nail is kept immersed in it?
74. Why should magnesium ribbon be cleaned
before burning in air?
75. Write a balance chemical equation for the
process of photosynthesis giving the physical states of all the substances
involved and the conditions of the reaction.
76. Zinc oxide reacts with carbon, on heating,
to form zinc metal and carbon monoxide. Write a balanced chemical equation for this reaction. Name (i)
substance oxidized, and (ii) substance reduced.
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