Monday, December 29, 2014

CBSE class 10 Physics Question paper 2013

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 individualresistances?
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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