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CURRENT ELECTRICITY

1. Why do copper or aluminium wires generally used for electrical transmission and distribution purposes. (b) Two wires, one of copper and other of manganin, have equal lengths and equal resistances. Which wire is thicker? Given that resistivity of copper is lower than that of manganin.

ans: (a) They have low resistance, so very small amount of energy is wasted in transmission. They are ductile so can be easily drawn into wires. b) Resistivity of manganin is very large, so it is thicker than copper.

2. Resistance of a metal wire of length 1m is 26V at 20oC. If the diameter of the wire is 0.3mm, what will be the resistivity of the metal at that temperature? Ans: 1.75 10- 6 m

3. (i) What precautions should be taken to avoid the overloading of domestic electric circuits?

(ii) An electric oven of 2 kW power rating is operated in a domestic electric circuit that has a current rating of 5A. If the supply voltage is 220V, what result do you expect? Explain.

Ans: (i) too many high power rating electrical appliances (electric iron, geyser, A.C.) should not be switched on at the same time. (ii) P 5 2 kW 5 2000 W . V = 220 V ; P = VI, I = P/V =9A. Current drawn is very high but the fuse is only of 5A - the fuse will blow off due to overloading - cutting off the power supply in this circuit.

4. Calculate the electrical energy consumed by a 1200W toaster in 20 minutes.

E 5 Power time 5 1200 W320360s 5 1200W31200s51.44 x 106J.

5. Why do the wires connecting an electric heater to the mains not glow while its heating element does?

Ans: The wires of the connecting cord of electric heater are made of Cu - negligible heat is produced in it - due to its extremely low resistance. The heating element of an electric heater - made of nichrome wire. It glows because large amount of heat is produced - due to its high resistance.

6. Draw a schematic diagram of a circuit consisting of a cell of 1.5 V, 10 V resistor and 15 V resistor and a plug key all connected in series.

7. Aluminum wire has radius 0.25 mm and length of 75 m. If the resistance of the wire is 10 V, calculate the resistivity of aluminum. Ans : use equation.

8. A graph between potential difference (V) and current (I) is given in figure.

· What is the relation between V and I.

· Find the resistance of the conductor using the graph.

9. Two resistances of 3 and 6are to be connected to a battery of 9V so as to obtain. (i) Minimum current. (ii) Maximum current in the circuit. (a) How will you connect the resistances to the battery in each case?

Calculate the total current flowing in the circuit in both cases.

Ans:

a) (i) I 5 V/R, Minimum current, Maximum resistance , R = R1+R2 ... Resistance are in series. ii) Maximum Current Minimum resistances of the combination. (Parallel) R =R 1R 2 / R1+R2. Parallel connection is to be made.

10. The voltage - current (V-I) graph of a metallic conductor at two different temperature T1 and T2 is shown below. At which temperature is the resistance higher.

11. In the circuit diagram shown, the two resistance wires A and B are of same area of cross section and same material, but A is longer than B. Which ammeter A1 or A2 will indicate higher reading for current? Give reason.

(i)

12. How would the reading of voltmeter (V) change if it is connected between B and C? Justify your answer.

Ans: R 5R1+R2+R3 51+2+3 56V. R2+R3 51+2+3 56V . V5IR .

13. What would be the reading of ammeter and voltmeter in the given circuit?

ans:2V

14. Two conducting wires of same material, equal length and equal diameter are first connected

In series and then in parallel. Compare the equivalent resistance in two cases.

Ans: Let the resistance of each wire be R. When connected in series, total resistance Rs5R1R =2R .When connected in parallel Rp=R2/2R=R/2.Rs=4Rp.

15. Resistances of three resistors are given as R1510V, R2520V and R3530 V. Calculate the effective resistance when they are connected in series. Also calculate the current flowing when the combination is connected to a 6V battery.

Ans: R 5R1 +R2 + R3, 5 10 + 20 + 30 560, I=v/R ,0.1A.

16. How would the reading of voltmeter (V) change if it is connected between C and D? Justify your answer .

17. A student performs an experiment with 4 cells and a resistance wire and an ammeter in series and observes that when the number of cells in the circuit is decreased, the value of current through the wire also decreases. Name the law that is involved in the experiment and write its mathematical form. V–I graph for two resistors R1, R2 and their series combination are shown in the figure below. Which graph represents the series combination of the other two? Give reason

Ans: Ohm’s law V/I =Constant or V/I = R A represents the series combination of B and C. Because in series resistance becomes greater. Since slope of A is greater than B and C, resistance of A is greater than B and C.

18. For the circuit shown in the diagram calculate: (a) the total effective resistance of the circuit (b) the total current in the circuit (c) the value of current through 20V resistor.

Ans: Effective resistance R2,3 5 R2 R3 / (R2 + R3) 5 (60 x 30 / 90) .Total effective resistance of the circuit, R 5 R1 + R2,3 5 20 + 20 5 40 ohm. Current in the circuit, I 5 V/R 5 10V/40 . Since 20 is in series, current remains the same i.e., 0.25 A.

19. What is the function of an earth wire? Why is it to necessary to earth metallic appliances?

Ans: Function: - To ensure the safe passage of excessive current into the ground during short circuiting. Low-resistance conducting path Any leakage of current to the metallic body, keeps its potential to that of earth and user may not get shock.

20. Give an example of a metal which is the best conductor of heat.

21. Name the physical quantity whose unit is volt/ampere. Ans: resistance (electrical)

22. Define 1 kWh. How is this unit of energy related to 1 joule?

ans: 1 kWh is the energy consumed when one kilowatt power is used for 1 hour . 1 kWh = 3.6 3 106 joule

23. Calculate the resistance of a wire, when a potential difference of 2 V is maintained for 1A

Current to flow through it.

24. The following circuit diagram shows the combination of three resistors R1, R2 and R3. Find (i) total resistance of the circuit, (ii) total current (I) flowing in the circuit and the (iii) potential difference across R1.

25. Two identical immersion heaters are to be used to heat water, in a large container. Which one of the following arrangement would heat the water faster? i) Connecting the heaters in series with the main supply, (ii) connecting the heaters in parallel with the main supply? Give reasons for your answer.

Ans: Let R be the resistance of the heater , R s=2R; Rp=R/2,

Is=v/2R / Ip=2v/R.

Hs=V2/2R

Hp=2V2/R

Faster heating in parallel connection.

26. Explain what is short circuiting and overloading in an electric supply

Ans(i) An electric circuit is said to be short circuited if live wire and neutral wire come in contact with each other. (ii) Overloading means to connect too many appliances with single socket and using faulty device in electrical circuit.

27. State Ohm’s law and write the condition in which this law is obeyed

Ans: Correct statement of Ohm’s law. Condition - constant temperature / No change in physical conditions

28. 28- In the circuit diagram shown, the two resistance wires A and B are of same length and same material, but A is thicker than B. Which ammeter A1 or A2 will indicate higher reading for current? Give reason.

ans: Ammeter, A1 will show higher reading. Because, as wire A is thicker than B, A has lesser resistance. So current drawn by A from the battery will be more and hence ammeter A1 will show higher reading.

29. Study the circuit diagram given below and calculate: (a) the value of current through each resister. (b) the total current in the circuit. (c) the total effective resistance of the circuit

30. (a) What is meant by electric resistance of a conductor ? (b) A wire of length L and resistance R is stretched so that the length is doubled and area of cross section halved. How will (i) resistance change and (ii) resistivity change?

Ans: Resistance: property of a conductor to resist the flow of charges through it. Try your self.

31. a) Draw a schematic labeled diagram of a domestic circuit which includes (i) a main fuse, (ii) a power meter, (iii) distribution box, and (iv) a power plug. (b) Why is it necessary to connect an earth wire to electric appliances having metallic covers?

Ans:The metallic body of electric appliances is connected to the earth by means of earth wire so that any leakage of electric current is transferred to the ground. This prevents any electric shock to the user. That is why earthing of the electrical appliances is necessary

32. 400 J of heat is produced in 4s in a 4 V resistor. Find potential difference across the resistor.

33. Which gas is filled in the electric bulb and why?

Ans: Argon or Neon. These are inactive or inert gases to prolong life of the filament .

34. Tungsten is used almost exclusively for filaments of electric bulb. List two reasons.

Ans: Resistivity of tungsten is very high as it is an alloy. It does not oxidize readily at very high temperature.

35. Determine the ratio of the (a) highest (b) lowest resistance that can be secured by combining four coils of resistance 4 V, 8 V, 12 V, and 24 V in an electric circuit. [Ans:24:1]

36. electric bulb draws a current of 0.8A from 250 V mains. The bulb is used on an average 8 hours a day, If energy costs Rs 3 per kWh, calculate the monthly bill for 30 days .

37. A wire of resistivity r‟ is pulled to double its length. What will be its new resistivity? [ try your self]

38. When do you say that the resistance of a wire is 1ohm ?

39. What precautions should be taken to avoid overloading of domestic electric circuits?

40. Two electric lamps rated 100 W, 220V and 25W, 220V are connected in parallel to a 220V supply. Calculate the total electrical current in the circuit.

41. Draw a schematic diagram of a circuit consisting of 24 V battery, a 10 ohm resistor, a 5 ohm resistors, a 1 ohm resistors, an ammeter and a plug key all connected in series. Find the ammeter reading and potential difference at the ends of 10 V resistor.

42. Why are the heating elements of electric toaster and electric iron made of an alloy rather than pure metal ? (b) An electric iron of resistance 20 V takes a current of 5 A. Calculate the heat developed in 30 seconds.

Ans: (a) (i) Alloys have higher value of resistivity. (ii) Alloys do not oxidize readily at high temperatures’) try your self H =I2Rt, [ans=15KJ]

43. Which is having more resistance a 220V, 100 W bulb or a 220V, 60 W bulb.

[60 W bulb because R;1/P. ]

44. - Why is it not advisable to handle domestic electrical circuit with wet hands?

Ans: Resistance of dry skin is more (about 50,000 ohms) than the resistance of the wet skin (10,000 ohms). The current will flow suddenly due to less resistance. Water - good conductor of electricity.

45. Three V-I graphs are drawn individually for two resistors and their series combination. Out of A, B, C which one represents the graph for series combination of the other two. Give reason for your answer.

Ans: We know that in series combination, resultant is always greater than the individual resistances. In the given graph, C is showing maximum resistance (as slope of V-I graph gives resistance), thus C represents the resultant series combination of the other two.

Note: set up a similar question for parallel connection draw V-I graph.

46. In the given circuit calculate : (i) the total resistance of the circuit, (ii) current flowing through the circuit, (iii) potential difference across the lamp and the resistor.

47. Study the following circuit and answer the following questions

State the type of combination of the two resistors in the circuit. (ii) How much current would flow through (a) 10 V resistor and (b) 15 V resistors? (iii) What would be the ammeter reading?

48. Four resistors of 2 V each are joined end to end to form a square ABCD. Calculate the equivalent resistance of the combination between any two adjacent corners.

Ans:

Let us consider the equivalent resistance between points A and B, Here three resistances of 2 Ohm each are in series. Equivalent resistance of these three 5 R15 21212 5 6 ohms ½ This combination is connected in parallel across the resistor of 2 ohm (R2 5 2 ohm) Thus, Required Equivalent resistance (R) ½ 1/ R 5 1/R1 11/R2 ½ 5 1/6 1 1/2 5 4/6 ½ R 5 1.5 ohm.

49. The components of an electric circuit are 0.5 m long nichrome wire XY, an ammeter, a voltmeter, four cells of 1.5 V each, rhoestat and a plug key. Draw a diagram of the circuit to study the relation between potential difference across the terminals X and Y of the wire and current flowing through it.

Ans;

50. (i) Parallel combination of resistors R1 and R2 and that of R3, R4 and R5 are connected to a battery of 12 V, an ammeter and plug key as shown in the circuit diagram. If R1510 V, R2540 V, R3530 V, R4520 V, and R5560 V calculate: (a) the total resistance in the circuit. (b) The total current flowing in the circuit.

51. What is meant by potential difference between two points?

Ans; Potential difference between two points in an electric field is the amount of work done to move a unit charge from one point to other.

52. Two identical resistors, each of resistance 20V are connected (i) in parallel (ii) in series, in turn, to a battery of 10 V. Calculate the ratio of power consumed in the combination of resistors in the two cases.

Remark:Short-circuiting : Resistance is very low, most of the current flows. When live wire comes in contact with neutral wire so that zero resistance path is achieved. Overloading: It occurs due to an accidental hike in the supply voltage. It is also caused by connecting too many appliance on a single socket .

53. B1, B2 and B3 are three identical bulbs connected as shown in the Figure. When all the three bulbs glow, a current of 3A is recorded by the ammeter A. Explain (i) How will the intensity of the glow of the other two bulbs change when the bulb B1 gets fused ? (ii) How will the reading of ammeters A1, A2, A3 and A change when the bulb B2 gets fused

· Other bulbs will glow with same brightness.

· When the bulbs are in parallel, wattage will be added (4.5 W) and the ammeter reading would be = 1.0 ampere 4 .5W /4.5V ..

· Since ammeter reading is 1.0 ampere resistance of the combination is 4.5v/1A=4.5ohm.

54. Explain the role of fuse in series with any electrical appliance in an electric circuit ? Why should a fuse with defined rating for an electric circuit not be replaced by one with a larger rating?

Ans:Fuse is used for protecting appliances due to short circuiting or overloading. The fuse is rated for a certain maximum current and blows off when a current more than the rated value flows through it. If a fuse is replaced by one with larger ratings, the appliances may get damaged while the protecting fuse does not burn off. This practice of using fuse of improper rating should always be avoided

55. Calculate the effective resistance between P and Q.

56. How many 40 W bulbs can be safely connected in a parallel circuit which is drawing current through a 5A fuse from a 220 V supply .

ans: P = VI = 220* 5 W , No. of bulbs = 2205/40=27.5 So 27 bulbs]

57. A wire of length l and area of cross-section A was drawn into a wire of double its length by melting it. If its original resistivity and resistance were r and R respectively, what will be its new resistivity and resistance?

ans: We know R 5r l/ A When a wire is doubled by melting, its length would become double and area of cross- section would be halved. i.e. length of wire 52 l and area of cross section 5A/2 1 Thus, we have R15r 2l/ A/2 54 r l /A 1 where R1 is the new resistance . Therefore, The new resistance of the wire is 4 R. 1 As resistivity of a material is the characteristic of a given material, hence it remains unchanged.

58. What is the difference between overloading and short circuiting ?

Ans:Overloading : - Beyond the maximum current estimation, if the appliances connected to the circuit draw more current, then it is called Overloading. Short Circuit :- Due to damaged or defective wiring live wire comes in the contact of neutral wire and the resistance of the circuit becomes zero. Therefore, large amount of current flows through the circuit and it get overheated and may catch fire.

59. Name the instrument used for measuring : (i) Potential difference (ii) Current .

60. Two electric bulbs A and B are marked 220 V, 40 W and 220 V, 60 W respectively. Which one of the two has the filament of larger resistance? Give reason for your answer. [R=V2/P]

61. What is an electric fuse ? Briefly explain its function.

Ans:An electric fuse is a device which is used ahead and in series of an electric circuit as a safety device to prevent the damage caused by short- circuiting or overloading of the circuit.

It is a small, thin wire of a material whose melting point is very low. If due to some fault electric circuit gets short-circuited, then a strong current begins to flow. Due to such strong flow of current the fuse wire is heated up and gets melted. As a result, the electric circuit is broken and current flow stops. Thus, possible damage to the circuit and appliances is avoided.

62. An electric heater draws a current of 10A when connected to a 200 V supply. What current will the heater draw when it is connected to 220 V supply.

63. Insulation cover of which color is conventionally used for earth wire? [ans: Green ]

64. A 9V resistance is cut into three equal parts and connected in parallel. Find the equivalent resistance of the combination.

ans: R = 9 V is cut into three equal parts. R a l, R1 =R2 = R3 =l/3,9/3=3, 3 ohm resistance are connected in parallel.

65. A torch bulb is rated 2.5 V and 750 mA. Calculate (i) its power, (ii) its resistance and (iii) the energy consumed if this bulb is lighted for four hours.

66. Series arrangements are not used for domestic circuits. List any three reasons.

ans: (i) In series arrangement same current will flow through all the appliances, which is not required. (ii) Total resistance of domestic circuit will be sum of the resistances of all appliances and current drawn by the circuits will be less. (iii) We cannot use independent On/Off switches with individual appliances. (iv) All appliances are to be used simultaneously even if we don’t need them.

67. a) what does the following circuit symbols represent?

(

Wires not connected (ii) Variable resistor/rheostat

68. The charge possessed by an electron is 1.6x10-19 coulombs. Find the number of electrons that will flow per second to constitute a current of 1 ampere. [ see text]

69. Name the physical quantity which is (i) same (ii) different in all the bulbs when three bulbs of :

· same wattage are connected in series

· same wattage are connected in parallel

· different wattage are connected in series

· different wattage are connected in parallel

Ans[

· current and voltage or PD (ii) nothing

· current and voltage (ii) nothing

· current (ii) voltage

· voltage (ii) current

70. Two devices of rating 44W; 220 V and 11W; 220 V are connected in series. The combination is connected across a 440 V mains. The fuse of which of the two devices is likely to burn when switch is on ? Justify your answer.

Ans:The fuse of device of rating 11W; 220V will burn, R = V2 /W Resistance of 11 W device will be four times that of the device of 44 W \ voltage across 11 W = 352 V voltage across 44W=88V. 352V across the device of 11W; 220 V rating is sufficient to burn the fuse of the device .

71. The wattage of a bulb is 24 W when it is connected to a 12V battery. Calculate its effective wattage if it operates on a 6 V battery (Neglect the change in resistance due to unequal heating of the filament in the two cases).

72. Five resistors are connected in a circuit as shown. Find the ammeter reading when circuit is closed.

73. Consider the following circuit diagram. If R15R25R35R45R553V, find the equivalent resistance of the circuit.

74. A circuit is shown in the diagram given below.

Find

· the value of R.

· the reading of the ammeter.

· the potential difference across the terminals of the battery

75. Consider the circuit shown in the diagram. Find the current in 3V resistor.

76. Draw a diagram to show a parallel combination of three resistors. Find the number of 176 V resistor connected in parallel to make a combination required to carry 5 A current from a source of 220 V. [R = 176 /n ]

77. Study the V-I graph for four conductors A,B,C and D having resistance RA, RB, RC and RD respectively, and answer the following questions

1. Which one of these is a best conductor ?

2. If all the conductors are of same length and same material, which is the thickest ?

3. If all the conductors are of same thickness and of same material which is the longest ?

4. If the dimensions of all the conductors are identical, but their materials are different which one would you use as(a) resistance wire (b) connecting wire

5. Which one of the following relations is true for these conductors (a) RA >RB>RC>RD (b) RA

6. If conductors A and B are connected in series and V-I graph is plotted for the combination, its slope would be (a) Less than that of A (b) more than that of A (c) between A and B

7. If conductors C and D are connected in parallel and V-I graph is plotted for the combination, its slope would be (a) Lesser than that of A (b) More than that of D (c) Between C and D (d) Between B and C .

78. Through which of the two wires the electric current will flow more easily (i) a thick wire or (ii) a thin wire of the same material, and of same length when connected to the same source

79. (a) the equivalent resistance, b) the current flowing through ammeter, (c) the potential difference across 10 V resistor

80. Name two safety measures commonly used in electric circuits and appliances. What precautions should be taken to avoid the overloading of domestic electric circuits ?

Ans:i) Fuse - cuts off high current 1 (ii) Proper earthing 1 (iii) Avoid overloading ]

81. An electric heater connected to a 220V line has two resistance coil of 22 ohms each. Calculate the current if these coils are used: a) separately (b) in series (c) in Parallel

82. State in brief the meaning of an electric circuit.

Ans:a closed conducting path through which electric charge may flow.

83. State the relationship between 1 ampere and 1 volt.

84. Name the property by virtue of which two conductors having identical structures offer different resistances to the flow of current when connected to the same source of electric current. [Resistivity ]

85. When connected to a 10 V battery a current of 1 ampere flows in a circuit containing an electric lamp and a conductor of 5 V in series. Calculate the resistance of the electric lamp. Now if a resistance of 10 V is connected in parallel with this series combination, what change (if any) in current flowing through 5 V conductor and potential difference across the lamp will take place ? Give reason. Draw circuit diagram.

Ans:(i)5V (ii) Hint - Calculate the total resistance of the circuit. There will be no change in current flowing through 5 V conductor. Also there will be no change in potential difference across the lamp either.

86. In an electric circuit state the relationship between the direction of conventional current and the direction of flow of electrons. [ try your self ]

87.

-

(i) Find the net resistance in the circuit. (ii) Redraw this circuit and show the position of the ammeter to find the current drawn from the battery.

Ans; REF in series with RAB ½ RED Series with RBC R2 = 3+3 = 6 V R1 and R2 are in parallel R = 6 + 6 = 12,

88. State the relationship between 1 volt and 1 joule.

89. Aluminium wire has radius 0.25 mm and length of 75 m. If the resistance of the wire is 10 V, calculate the resistivity of aluminum

90. A piece of wire of resistance 20 V is drawn out so that its length increases to twice its original length. Calculate the resistance of the wire in the new situation.

91. (a) What is the total resistance of n resistors each of resistance ‘R’ connected in : (i) Series (ii) Parallel [(a) Rs5( R1R1 ......... R)5nR , RP= R/ n ]

92. An electric oven of 2 kW power rating is operated in a domestic electric circuit of that has a current rating 5A. If the supply voltage is 220V, what result do you expect? Explain.

93. State in brief the meaning of a variable resistor. Draw a circuit diagram to illustrate its function specially in the study of variation in current with potential difference across a resistor.

Ans: A device to regulate current without changing the voltage source in an electric circuit.

(i)

94. A fuse wire melts at 5A. If it is desired that the fuse wire melt at 10A, then whether the new fuse wire should be of smaller or larger radius than the earlier one ? Give reason for your answer.

Ans:Radius be increased. Reason : Resistance decreases. So heat produced is less and it will allow larger current to flow.

95. Two heaters rated 750 W, 200 V and 1000 W, 200 V are connected in parallel across 200 V supply. Calculate total power consumed. [P=P1+P2=1750 W. ]

96. a) Which effect of the electric current is utilized in the working of an electrical fuse ? (b) Is fuse connected in series or in parallel in household circuits?

Ans:[(a) Heating effect –(b) Fuse is connected in series

97. Keeping the potential difference constant the resistance of an electric circuit is doubled. State the change in the reading of an ammeter connected in the circuit.[try your self]

98. How would the reading of (V) change if it is connected between C and D ? Justify your answer

ans; 1V

99. The resistance of a resistor is kept constant and the potential difference across its two ends is decreased to half of its former value. State the change that will occur in the current through it.

100. An electric resistor of resistance 20V draws a current of 5A. Calculate the heat produced by it in 30 seconds.

101. A thick wire and a thin wire made from same material and of same length are connected one by one to the same source. In which case a larger current will flow in the circuit ? Justify your answer.

Ans: A larger current will flow through the circuit when thick wire is connected to it. Since, . R1/A. . The resistance of thick wire will be lower as compared to thin wire. So a larger current will flow through the circuit with thick wire

102. An electric bulb is marked 60W. What does this mean? How much energy does it consume if used for 1 hour?

Ans:This means that 60J of energy is used per second. 1 Energy = Pt = 60x1 h = 60 Wh =0.06 kWh

103. -What are the advantages of connecting different electrical appliances in parallel ? Mention any three advantages.

Ans: 1)Same voltage as that of the power line.2) Overall resistance is reduced - current from the power supply is high. 3)If one electrical appliance stops working all other appliances keep working normally.

104. A piece of wire of resistance R is cut into two equal parts. If these two parts are now connected in parallel, then state how the resistance and the resistivity of the combination will change. Justify your answer.

Ans:R/4, ii) Resistivity is the property of the material.

105. 109-Why do the wires connecting an electric heater to the mains not glow while it’s heating element does?

106. Two conducting wires of same material, equal length and equal diameter are first connected in series and then in parallel. Compare the heat produced by the combination of resistances in two cases.

Ans:Let the resistance of each wire be ‘R’ ½ When connected in series total resistance Rs 5 R1R 5 2R When connected in parallel the total resistance, Rp= R/ 2 , H= V2t/ R .

107. State the change in the ammeter reading observed when a resistance wire in a circuit is replaced by a wire of same material and same length but comparatively double cross-sectional area keeping the source of potential difference constant.

108. Distinguish between an open and a closed circuit

Ans:. closed circuit-Key is closed-current flows continuously. Open circuit-Key is open-no flow of current.

109. A copper wire has a radius of 1mm and resistivity of 1.631028 Vm. What will be the length of this wire required to make its resistance 10V ?

110. What would be the reading of ammeter and voltmeter in the given circuit?

111. Name the physical quantity which is same in all the resistors when they are connected in series. [I]

112. Two students perform experiments on two given resistors R1 and R2 and plot the V - I graphs shown by diagram 1 and 2 If R1> R2, which of two diagrams correctly represent the situation on the plotted curves ? Justify your answer.

113. Two identical immersion heaters are to be used to heat water, in a large container. Which one of the following arrangement would heat the water faster : (i) connecting the heaters in series with the main supply, (ii) connecting the heaters in parallel with the main supply ? Give reasons for your answer.

Answer:H=V2/R parallel connection Faster (4 times) heating in parallel connection.

114. Draw circuit symbols of the following components

Variable resistance or rheostat (ii) Plug key or switch (closed)

115. A wire of resistance R is cut into three equal parts. (i) Find the value of resistance of each part in terms of the original resistance R?

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