Wednesday, June 26, 2013

classes IX and XI for the academic year 2013-14: Problem Solving Assessment

Problem Solving Assessment for classes IX and XI for the academic year 2013-14 will be held on 10th January, 2014 for summer closing schools) and on October 19, 2013 ( for winter closing schools). Problem Solving Assessment (PSA) for students of classes IX and XI was conducted by the Board on 16th February, 2013 for the previous academic session. It was primarily aimed at assessing students’ reasoning skills, analytical skills, thinking skills and other higher order  mental abilities. However, since winter closing schools were closed during the months of January and February due to severe cold conditions, this test could not be conducted for these schools.
PSA Sample Papers 
1. PSA Sample Papers for class IX
2. PSA Sample Papers for class XI
Salient features of this test will be as follows:

  • It will be compulsory for all students of classes IX and XI.
  • It will comprise of 60 items of MCQ type and will carry 60 marks.
  • The examination will be held from 10.00 AM to 12.00 Noon.
  • There is no specific syllabus for this test. It will assess life skills related to the following elements:
  1. Qualitative Reasoning
  2. Quantitative Reasoning
  • The items will incorporate assessment of 21st Century skills such as Creative Thinking, Decision-making, Critical Thinking, Problem Solving and Communication skills that lead to greater success at higher education as well as real life situations. These items will be assessing students’ ability to process, interpret and use information rather than merely assessing students’ prior subject knowledge.
  • The assessment in language will contain items that will assess grammar, usage, vocabulary in context and passage-completion.
  • The items will be prepared in Hindi as well as English.
  • PSA score will be counted towards FA4 which is 10% of total assessments for class-IX. This score will be reflected equally in one language (English or Hindi), Mathematics, Science and Social Science. Class-XI students will be issued a separate certificate for the same.
  • All those students of classes X and XII (who appeared in PSA while studying in classes IX and XI during the previous session) who wish to improve in PSA may be allowed to do so. Related information may be indicated clearly at the time of submission of the List of Candidates for 2014 annual examination.
  • There will be no separate registration for appearing in PSA.

  1. Language conventions [English]

The schools may contact Dr. Sadhana Parashar, Director (ART &I) at sadhanap.cbse@nic.in or Mr. R.P. Sharma, Consultant at science.cbse@gmail.com for any further clarifications if, need be.
Source: http://www.cbseacademic.in and www.mycbseguide.com/   
Related post:
CBSE plans to introduce Problem Solving Assessment for classes IX, XI   View 

Monday, June 24, 2013

CBSE SAMPLE PAPER 8TH MATHEMATICS SA-1

8th Maths Sample paper for  Practice 

1. What least number must be subtracted from 7250 to get a perfect square? Also, find the square root of this perfect square

2. What is the least number by which 12348must be divided to obtain a perfect square?

3. Find the cost of erecting a fence around a square field whose area is 9 hectares if fencing costs Rs 3.50 per metre

4. Find the least number of six digits which is a perfect square. Find the square root of this number.

5. Divide
(1) x3 - 1 by x - 1 (2) 7 +15x -13x2 +5x3 by 4 - 3x + x2

6. . x + y + z = 0, prove that x 3+ y3 + z3 = 3xyz. Or, Factorize : (a8 – b8)

7. If ( x2 + 1/X2) = 83 . Find X3- 1/X3

Or, , Factorize (i) 25a² – 4b² + 28bc – 49c² (ii) 5y² – 20y – 8z + 2yz

8. A motor boat covers a certain distance downstream in a river in 5 hours. It covers the same distance upstream in 6 hours. The speed of water is 2 km/hr . Find the speed of the boat in still water.

9. Three prizes are to be distributed in a quiz contest. The value of the second prize is five sixths the value of the first prize and the value of the third prize is four – fifths that of the second prize. If the total value of three prizes is Rs. 150, find the value of each prize.

10. (a) Each side of a triangle is increased by 10 cm. If the ratio of the perimeters of the new triangle and the given triangle is 5 : 4, find the perimeter of the given triangle

(b) . The difference between two positive integers is 36. The quotient, when one integer is divided by the other is 4. Find the two integers.

11. Factorize

(1) x4 – (y + z)4 (2) y2 –7y +12 (3) 6xy – 4y + 6 – 9x  (4) a4 – 2a²b² + b4 (5) (x² – 2xy + y²) – z² 

8th Factorization

1. Factorization

(1) (a + b ) (1 – c ) – (b + c ) ( 1 – c ) (2) 1 6 a2 + 40 a b + 25 b2 (3) 4x2/9 - 2/3 x y + y2 /4

(4) 5x2yz - 5 x3y (5) 18 q2 + 338 p2 - 1 5 6 p q (6) -108 x2 - 363 y2 + 369 x y

2. Factorize

(1) 16- 4x2 (2) 20 x3 – 45 b4x (3) 4a2 – 9 b2 – c2 - 6bc

4) 25 ( x + 2y )2 - 36 (2x-5y)2 (5) a2 + 2 a b + b2 – c2 -2cd –d2

3. Factorize using a2+b2+c2 +2ab+2bc+2ca

(1) x2 + y2 + 25 z2 – 2 x y – 10 y z + 10 z x (2) 9x2 + 4y2 + 49z2 – 12 x y + 28 y z – 42 z x

(3) 4x6 + 9y6 + 16 x 6 + 12 x3 y3 + 16 x3 z3 + 24 y3z3 (4) a8 + 256 b8 + 96 a4b4-16a3b2 – 256a2b6

4. Factorize (x + a) (x + b) = x2 + (a + b) x +a b

(1) x2+7x+ 10 (2) x2+x-20 (3) x2-4x-21 (4) 15x2 + 13x + 2 (5) -6x2 - 13x+5

5. Factorize

(1) 125 a3 + 150 a2b + 60 ab3 + 8ab3 (2) x6 – 12 x4 b4 c + 6a2b5c2 + b6c3 (3) 81a3 + 24b3

(4) 64a3b2 – 125 b5 (5) 16 a3 – 54 b3 (6) 8X + 1

(7) a3 - 27b3 (8) 729a6 - 1 (9) 8m3 + 64 (10) 1000 – 343 a9

6. Find the following products:

(1) (9m + 2m )( 81m2 -18mn + 4n2) (2) (5 - 2x ) (25 +10x + 4x2) (3) (3 + 5/x ) ( 9 – 15/x + 25/x2)

7. Find the value of 27x2 + 64y2 + 36xy(3x + 4y) , when x = 5 and y = -3.

8. Using the identity (x + a) (x + b) = x2 + (a + b)x + a b, evaluate 98 x 97

9. x + y + z = 0, prove that x 3+ y3 + z3 = 3xyz.

10. Factorize

(1) m4 – 256 (2) y2 –7y +12 (3) 6xy – 4y + 6 – 9x

(4) x4 – (y + z)4 (5) a4 – 2a²b² + b4 (6) (l + m) ² – 4lm

(7) (x² – 2xy + y²) – z² (8) 25a² – 4b² + 28bc – 49c² (9) 5y² – 20y – 8z + 2yz

(10) a8 – b8

8th Linear Equations In One and two Variable

1. The perimeter of a rectangular swimming pool is 154 metres. Its length is 2m more than twice its breadth. What are the length and breadth of the pool.

2. Sum of two numbers is 95. If one exceeds the other by 15 find the numbers.

3. Two numbers are in the ration 5:3. If they differ by 18, find these numbers

4. Three consecutive integers add up to 51. What are these integers?

5. The sum of three consecutive multiples of 8 is 888. Find the multiple.

6. Three consecutive integers are as such when they are taken in increasing order and multiplied by 2, 3, and 4 respectively, they add up to 74. Find these numbers.

7. The number of boys and girls in a class is in 7:5 ratio. The number of boys is 8 more than that of girls. Fin their numbers.

8. The ages of Rahul and Haroon are in the ratio of 5:7. Four years from now sum of their ages will be 56 years. Find their present age.

9. Baichung’s father is 26 years younger than Baichung’s grandfather and 29 years older than Baichung. The sum of their ages is 135. Find their ages.

10. Fifteen years from now Ravi’s age will be 4 times his current age. What is his current age.

11. Lakshmi is a cashier in a bank. She has notes of denominations of Rs. 100, 50 and 10 respectively. The ratio of number of these notes is 2:3:5 respectively. The total cash with Lakshmi is 4,00,000. How many notes of each denomination does she have?

12. I have total Rs 300 in coins of denominations of Rs.1, Rs.2, and Rs. 5.The number of Rs. 2 coins is 3 times the number of Rs. 5 coins. The total number of coins is 160. How many coins of each denomination are with me.

13. The organizers in an essay competition decide that winner will get a prize of Rs. 100 and a participation who doesn’t win gets a prize of Rs. 25. The total prize money distributed is Rs. 3,000. Find the number of winners if the total number of participants is 63.

14. If in a rational number denominator is greater than numerator by 8. If you increase the numerator by 17 and decrease the denominator by 1, you get 3/2 as result. Find the number.

15. Amina thinks of a number and subtracts 5/2 from it. She multiplies the result by 8. The final result is 3 times her original number. Find the number

16. A positive number is 5 times another number. If 21 is added to both the numbers then one of the new numbers becomes twice of another new numbers. Find the original numbers.

17. Sum of the digits of a two digit number is 9. When we interchange the digits the new number is 27 greater than the earlier number. Find the number.

18. One of the digits of a two digit number is three times the other digit. If you interchange the digits and add the resulting number to original number you get 88 as final result. Find the numbers.

19. Sahoo’s mother’s present age is six times Sahoo’s present age. Five year from now Sahoo’s age will be one-third of his mother’s age. Find their current age.

20. There is a narrow rectangular plot. The length and breadth of the plot are in the ratio of 11:4. At the rate of Rs. 100 per metre it will cost village panchayat Rs.75000 to fence the plot. What are the dimensions of the plot.

21. Hasan buys two kinds of cloth materials for school uniform. Shirt material cost him Rs. 50 per metre and trousers material cost him Rs. 90 per metre. For every 2 metres of the trousers material he buys 3 metres of shirt material. He sells them at 12% and 10% profit respectively. His total sale is Rs. 36,660. How much trousers material did he buy? ( 200m)

22. Half of a herd of deer are grazing in the field and three fourths of the remaining are playing nearby. The rest 9 are drinking water from the pond. Find the total number of deer in the herd.

23. A grandfather is 10 times older than his granddaughter. He is also 54 years older than her. Find their age.

24. A man’s age is three times his son’s age. Ten years ago his age was five times his son’s age. Find their current age.

25. Hari and Harry’s age are in the ratio of 5:7. Four years later the ratio of their ages will be 3:4. Find their current age.

8th Algebraic Expression

1. If ( x + 1 / x ) = 4, Find the value of ( x2 + 1/x2 ) and (x4 + 1/x4 )

2. If ( x - 1/ x ) = 3 .Find the value of (x3 + 1/x3 )

3. Find the remainder obtained by dividing x3 + 3 x2 - 5x + 4 by x + 1

4. Evaluate using algebraic identities (54)2 ; (78)2; (999)2

5. If x - y = 7, x y = 9 Find the value of x2 + y2

6. If x + y = 12 , x y = 27 Find the value of x3 + y3

7. If a2 + b2 + c2 =20 , a + b + c = 6 find a b + b c + ca

8. If ( x2 + 1 / x2 ) = 83 . Find (x3 - 1 / x3 )

9. What must be subtracted from 4p2 - 2pq - 6q2 - r +5 to get - p2 + p q - 8q2 - 2r+5

10. Factorise a3 + b3 + c3 - 3 a b c

11. Devide

(1) x3 - 1 by x - 1

(2) 7 +15x -13x2 +5x3 by 4 - 3x + x2

12. Evaluate

(1) 1.5 3 - 0.93 - 0.63

(2) (a - b) 3 + (a + b) 3

(3) (x + 2y -3z)2 + (x - 2y +3z)2

13.If (x4 + 1 / x4 ) = 47 find the value of (x3 + 1 / x3 )

14. Find the product of

(1) (x4 + 1/x4 ) and ( x + 1/x )

(2) (2x2 + 3x - 7)(3x2 -5x - 4)

15.Two adjacent side of a rectangle are 5x2-3y2 and x2 - 2xy Find its perimeter

16.The perimeter of a triangle is 6p2 - 4p + 9 and two of its adjacent side are

p2 - 2p + 1 and 3 p2 - 5p + 3. Find third side of triangle.

17. Find the least no. of 5 digits which is perfect square.

18. Find the greatest num. of 6 digits which is perfect square.

19. Evaluate

(1) (5-1 x 3-1 )-1 x 6-1 (2) ( 23x+1 +10 ) / 7 = 6

(3) [52x+1]/ 25 = 125 (4) (4/9)4 x (4/9) - 7 = (4/9) 2x – 1
Compound Interest:

10th Maths Similar triangle Guess Paper For CBSE Exam SA-1

10th Triangle (Similarity) Practice Questions For SA-1 By JSUNIL
Similar figures: “Two similar figures have the same shape but not necessarily the same sizes are called similar figures. “ This verifies that congruent figures are similar but the similar figures need not be congruent.
Conditions for similarity of polygon: Two polygons of the same number of sides are similar, if
(i) Their corresponding angles are equal and
(ii) Their corresponding sides are in the same ratio (or proportion).
Note: The same ratio of the corresponding sides is referred to as the scale factor (or the Representative Fraction) for the polygons.
Equiangular triangles:  If corresponding angles of two triangles are equal, then they are known as equiangular triangles.
A famous Greek mathematician Thales gave an important truth relating to two equiangular triangles which is as follows: “The ratio of any two corresponding sides in two equiangular triangles is always the same.”
Q. The Basic Proportionality Theorem (now known as the Thales Theorem) :  “If a line is drawn parallel to one side of a triangle to intersect the other two sides in distinct points, the other two sides are divided in the same ratio. “ [Prove it.]
Q. The converse of The Basic Proportionality Theorem:  If a line divides any two sides of a triangle in the same ratio, then the line is parallel to the third side. [Prove it by contradiction methods]
Q. In a triangle ABC, E and F are point on AB and AC and EF || BC. Prove that   AB/AE = AC/AF
Q. Prove that a line drawn through the mid-point of one side of a triangle parallel to another side bisects the third side.
Q. Prove that the line joining the mid-points of any
two sides of a triangle is parallel to the third side.
Q. In a triangle ABC, E and F are point on AB and AC Such that AE/EB = AF/FC and <AEF =<ACB. Prove that ABC is an isosceles Triangle.
Q. In a trapezium ABCD , AB || DC and  E and F are points on non-parallel sides AD and BC respectively such that EF is parallel to AB .Show that AE/ ED = BF /FC [join AC to intersect EF at G]
Q. In a trapezium ABCD  , AB || DC and its diagonals intersect each other at the point O. Show that  AO/ BO = CO/DO
Q. If the diagonals of a quadrilateral divide each other proportionally, then it is a trapezium.
Q. In ΔABC, DE || BC
(a) IF AD /DB = 2/3 and AC = 18cm, find AE.
(b) IF AD = x, DB = x – 2 , AE = x + 2, EC = x -1, find x.
(c) If AD = 8cm, AB = 12cm, AE = 12cm, find CE.

Q. In the given figure, AB || DC. If EA = 3x - 19, EB = x - 4, EC = x - 3 and ED = 4, find x.
Download Full Pdf File :  DOWNLOAD

Saturday, June 22, 2013

Sample Paper Of Class 8th maths and science

 Sample Question Papers Class-VIII Summative Assessment I (Year 2013 - 14) 
Mathematics Question Papers Class-VIII Summative Assessment I
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Science and Technology Question Papers Class-VIII Summative Assessment I
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Question Papers Class-VIII Summative Assessment II (Year 2013 - 14)

Mathematics Question Papers Class-VIII Summative Assessment II
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Science and Technology Question Papers Class-VIII Summative Assessment II
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Fore more sample paper visit   8th Maths Sample papers

Monday, June 10, 2013

Class Wise Distribution of Syllabus and Worksheets (2012-13) for class 1 to 8th



The page displays syllabus of all the classes of Government Schools of the DoE. The syllabus has been divided according to the weeks and is available separately for each class from VI to XII.

This is a unique attempt to ensure the same level of teaching learning process throughout the department in all the schools irrespective of their location and the availability of staff.

It also helps in objective inspections on the basis of the syllabus covered in a particular class within a particular time frame. This attempt also reduces the workload on the teachers while devising and forecasting their lesson plans for the forth coming week in advance as it is already available online. It also ensures uniformity in teaching process at all places at all times.

Week wise Syllabus (2013-14) Class Wise Distribution of Syllabus 
Week wise Syllabus (2013-14)
Worksheets (2012-13)
 Class - I New



 Class - IV New
 Class - I New
Class - V New
  Class - VI New
Class -IX New
Class - X New
              

Source: http://www.edudel.nic.in/asg_file/classwise_distribution_new.htm

for class10: Magnetic Effects of Electric Current - CBSE Board Questions

Sadhana Devi Vidyapith Assignment SA-1 + Chapter: Magnetic Effects of Electric Current                                             

Section-A [1-marks]
1. What does the direction of thumb indicate in the right-hand thumb rule?

2. What is the frequency of alternating current in India?

3. How will you use a solenoid to magnetize a steel bar?

4. An alternating electric current has a frequency of 50 Hz. How many times does it change its direction in one second?

5. Name devices which produce: (i) alternating current, (ii) direct current.

6. Name the physicist who discovered the magnetic effect of the electric current.

7. A straight copper conductor is held parallel to the axis of a freely suspended magnetic needle such that the conductor is under the needle and the current is flowing from south to north. In which direction the north of magnetic needle will move?

8. If a copper conductor carrying a current is held in north-south direction, in which direction will its magnetic field act?

9. Why does the strength of electromagnet increase, when its soft iron core is laminated?

10. Why does a conductor carrying current experiences force when held in a magnetic field at right angles to it?

Section-B [2 marks] Read full post

Monday, June 3, 2013

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 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.