A Question Bank provides you a plenty of good questions for practice and meaningful discussion with your peers. It saves time and make you confident in the subject. The following is the Question Bank on Electricity Class 10 standard.
1. What does an electric circuit mean?
2. Define the unit of current.
3. Calculate the number of electrons constituting one coulomb of charge.
4. A current of 0.5 A is drawn by a filament of an electric bulb for 10 minutes. Find the amount of charge that flows through the circuit. (Ans. 300 C)
5. Name the instrument used to measure electric current in a circuit. How is this instrument connected in a circuit? Draw a simple circuit diagram to explain your answer.
6. Which particles constitute electric current in a metallic conductor?
7. Name two units for expressing the small values of current. Also write their symbols. How are these units related to ampere?
8. Name a device that helps to maintain potential difference across a conductor.
9. What is meant by saying that potential difference between two points is 1V?
10. Write the relation which states the relation between potential difference and work done.
11. How much energy is given to each coulomb of charge passing through a 6V battery?
12. How much work is done in moving a charge of 2 C across two points having a potential difference of 12 V?
13. Name the device that measures the potential difference across two points in an electric circuit. How it is connected in an electric circuit?
14. Name and state the law which relates the current in a conductor to the potential difference across a conductor and the current flowing through it.
15. Define the SI unit of resistance.
16. (a) How much current will an electric bulb draw from a 220 V source, if the resistance of the bulb filament is 1200 Ω? (Ans. 0.183 A)
(b) How much current will an electric heater coil draw from a 220 V source, if the resistance of the heater coil is 100 Ω? (Ans. 2.2 A)
17. The potential difference between the terminals of an electric heater is 60 V when it draws a current of 4 A from the source. What current will the heater draw if the potential difference is increased to 120 V? (Ans. 8 A)
18. A wire of given material having length l and area of cross-section A has a resistance of 4 Ω. What would be the resistance of another wire of the same material having length l/2 and area of cross-section 2A? (Ans. 1 Ω)
19. On what factors does the resistance of a conductor depend?
20. Will current flow more easily through a thick wire or a thin wire of the same material, when connected to the same source? Why?
21. Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?
22. Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?
23. When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor. (Ans. 4800Ω)
24. Why is the tungsten used almost exclusively for filament of electric lamps?
25. Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
26. How does the resistance of a wire vary with its area of cross-section?
27. Why copper and aluminium wires are usually employed for electricity transmission?
28. Keeping the potential difference constant, the resistance of a circuit is doubled. By how much does the current change?
29. Give two examples of materials which are (i) good conductor (ii) resistor (iii) insulator (iv) poor conductor.
30. Why do electricians wear rubber hand-gloves while working with electricity?
31. Name the device used to change resistance in a circuit to regulate current without changing the voltage source.
32. What is nichrome? State its one property and one use.
33. Define resistivity. What is its SI unit? On what factor does it depends?
34. A wire of resistance 20 Ω is stretched to double its length. What will be its new (i) resistivity (ii) resistance? (Ans. New R = 80 Ω)
35. The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below –
I (amperes) 0.5 1.0 2.0 3.0 4.0
V (volts) 1.6 3.4 6.7 10.2 13.2
Plot a graph between V and I and calculate the resistance of that resistor.
36. Write the use of following components in an electric circuit
(a) Cell/battery
(b) Ammeter
(c) Connecting wires
(d) Switch/plug key
37. A wire of resistance R is cut into five equal pieces. These five pieces of wire are then connected in parallel. If the resultant resistance of this combination be R then the ratio of resultant to the original will be?
38. A radio set draws a current of 0.36 A for 15 minutes. Calculate the amount of electric charge that flows through the circuit. (Ans. 324 C)
39. Potential difference between two points of a wire carrying 2 ampere current is 0.1 volt. Calculate the resistance between these points. (Ans. 0.05Ω)
40. A simple electric circuit has a 24 V battery and a resistor of 60 ohms. What will be the current in the circuit? The resistance of the connecting wires is negligible. (Ans. 0.4 Ω)
41. Find resistance between A and B in following network
42. A resistance of 6 ohms is connected in series with another resistance of 4 ohms. A potential difference of 20 volts is applied across the combination. Calculate the current through the circuit and potential difference across the 6 ohm resistance. (Ans. 2 A, 12 V)
43. Calculate the work done in moving a charge of 5 Coulombs from a point at a potential of 210 Volts to another point at 240 Volts. (Ans. 150 J)
44. How many electrons pass through a lamp in one minute if the current be 200 mA? (72 x 10^18)
45. Calculate the current supplied by a cell if the amount of charge passing through the cell in 4 seconds is 12 C ? (Ans. 4 A)
46. A 2 Volt cell is connected to a 1 Ω resistor. How many electrons come out of the negative terminal of the cell in 2 minutes? (Ans. 1440 x 10^18)
47. A torch bulb when cold has 1Ω resistance. It draws a current of 0.3 Ampere when glowing from a source of 3 V. Calculate the resistance of the bulb when glowing and explain the reason for the difference in resistance. (Ans. 10Ω)
48. A current of 0.2 Ampere flows through a conductor of resistance 4.5 Ω. Calculate the potential difference at the ends of the conductor. (Ans. 0.9 V)
49. You have two metallic wires of resistances 6 ohm and 3 ohm. How will you connect these wires to get the effective resistance of 2 ohm?
50. State Ohm’s law. “The resistance of a conductor is 1Ω.” What is meant by this statement?
51. Prove that 1 J is equivalent to 1 Vx A x s.
52. How long does it take a current of 5.0 mA to deliver 15 C of charge? (Ans. 3000 s)
53. What is the potential difference between two points if 1.0 kJ of work is required to move 0.5 C of charge between the two points? (Ans. 2000 V)
54. What is the voltage of a source which provides 12.0 J to each Coulomb of charge present?
55. What is the potential difference between two points when a charge of 80.0 C has 4.0 x 10^3J of energy supplied to it as it moves between the two points? (Ans. 50 V)
56. There is a current of 0.50 A through an incandescent lamp for 5.0 min, with a voltage of 115 V. How much energy does the current transfer to the lamp? What is the power rating of the lamp? (Ans. 17250 J, 57.5 W)
57. If there is a current of 2.0 A through a hair dryer transferring 11 kJ of energy in 55 s, what is the potential difference across the dryer? (Ans. 100 V)
58. An electric drill operates at a potential difference of 120V and draws a current of 6.0 mA. If it takes 40 s for the drill to make a hole in a piece of wood, how much energy is used by the drill? (Ans. 28.8 J)
59. An electric toaster operating at a potential difference of 115 V uses 3220 J of energy during the 20 sec it is on. What is the current through the toaster? (Ans. 1.4 A)
60. A motor draws a current of 2.0 A for 20.0 sec in order to lift a small mass of 500 g. If the motor does a total of 9.6 kJ of work calculate the voltage drop across the motor. (Ans. 240 V)
61. In a lightning discharge, 30.0 C of charge moves through a potential difference 108 V in 20 minute. Calculate the current of the lightning bolt. (Ans. 0.025 A)
62. How much energy is gained by an electron accelerated through a potential difference of 3.0 x 10^2 V? (4.8 x 10-17 J)
63. A 12V car battery can provide 6 A for 1.0 h. how much energy is stored in the battery? (Ans. 259200 J)
64. a) Describe the difference between current in a series circuit and current in a parallel circuit.
b) Describe the difference between voltage in a series circuit and voltage in a parallel circuit.
65. Draw a schematic diagram of the following circuit: One power source and a resistor are connected in series with a combination of 3 light bulbs connected in parallel with each other. Include a fuse, 4 switches, a voltmeter, and an ammeter. The fuse should protect the whole circuit, one switch should shut off the whole circuit and the other switches should control the individual bulbs. The ammeter should read current drawn from power source and the voltmeter the voltage of the resistor.
66. Describe the effect on the rest of the bulbs in the above problem when one burns out. Will the remainder glow brighter or dimmer? What will be the effect on the source?
67. a) What is a short circuit? b) Why is it dangerous? c) Give two ways to protect against short circuits.
68. A conductor has a length of 2.0 m and a radius of 3.0 mm. If the resistance is R = 100 Ω, calculate the new resistance if the same material has:
a) length = 6.0 m and r = 6.0 mm (Ans. 75 Ω)
b) length = 1.0 m and r = 1.0 mm (Ans. 450 Ω)
69. List two ways to increase the current drawn by a circuit.
70. A voltmeter measures a voltage drop of 60.0 V across a heating element while an ammeter reads the current through it as 2.0 A. What is the resistance of the heating coil? (Ans. 30Ω)
71. How much current flows through a 7.5 W light bulb with a potential difference of 1.5 V? (Ans. 5A)
72. A set of 6 identical motors are connected in series to a 120 V source drawing 1.0 A of current. Find:
a) R total
b) R of each motor
c) Voltage drop across each load. (Ans. 120Ω, 20Ω and 20 V)
73. A set of 6 identical motors are connected in parallel to a 150 V source drawing 1.2 A of current. Find:
a) R total
b) R of each motor
c) Current through each motor
d) Voltage drop across each load. (Ans. 125Ω, 750Ω, 0.2 A and 150 V)
74. Do resistors in parallel increase or decrease total resistance?
75. What resistance must be added in series to a circuit containing a 45 ohm resistor in order to draw 2.0 A of current from a 120V source? (Ans. 15 Ω)
76. What makes the electric charge to flow?
77. The V–I graph is a straight line that passes through the origin of the graph. What do you conclude from this observation?
78. Define the commercial unit of energy. Relate it to joules.
79. Discuss the activity to show that resistance of a conductor depends on its length and area of cross section.
80. Which common factor affects both resistance as well as resistivity?
81. Alloys are commonly used in electrical heating devices. Why?
82. It is impracticable to connect an electric bulb and an electric heater in series. Why?
83. What is heating effect of electric current? Name the various devices in which this effect is utilized.
84. State the Joule’s law of heating. Derive the expression for the same.
85. Which effect of current is responsible for the glow of an electric bulb? Explain.
86. The bulbs are usually filled with few gases. Name those gases. Also discuss the cause for the same.
87. Which metal is used as the filament of an electric bulb and why?
88. How does a fuse work in the electric circuit?
89. Which materials are preferred for a fuse wire and why?
90. Give the ratings of various fuses used in the domestic circuit.
91. A torch bulb is rated at 3V and 600mA. Calculate it’s a) Power b) Resistance c) Energy consumed if it is lighted for 4 Hrs. (Ans. 1.8 W, 5 Ω, 0.0072kWh/25920 J)
92. Which will offer more resistance a 50W lamp or 25W lamp bulb and how many times? (ans. 25 W, 2 times)
93. Why should the heating element of an electric iron be made of iron, silver or Nichrome wire?
94. If a wire is stretched to triple its original length, what happens to its resistivity?
95. Two identical resistors each of resistance 10 ohm are connected 1) in series 2) in parallel, in line to a battery of 6volts. Calculate the ratio of power consumed in the combination of resistors in the two cases. (Ans. 1:4)
96. A bulb is rated at 220V- 100W. What is its resistance? Five such bulbs burn for 4 hrs. What is the energy consumed? Calculate the cost if the rate is Rs. 5 per unit? (Ans. 484 Ω 2kWh, Rs 10)
97. Two lamps rated 100W, 220V and 120W, 220V are connected in parallel to 220V supply. Calculate the total current through the circuit. (Ans. 1 A)
98. How does the resistance of wire change when 1) Its length is doubled 2) Area is doubled?
99. A wire of resistance 10ohm is bent in the form of a closed circle. What is the effective resistance between the two points at the end of any diameter of the circle? (Ans. 2.5 Ω)
100. When resistances are connected in series, which physical quantity remains constant?
101. When resistances are connected in parallel, which physical quantity remains constant?
102. Resistance of an incandescent filament of lamp is more than that when it is at the room temperature. Why?
103. The length of a wire is doubled and its cross sectional area is also doubled. What is the change in its (i) resistivity (ii) resistance?
104. Name two characteristics of a heating element wire.
105. For an electric iron of 1kW rating at 220V, fuse of how much capacity is to be used? (Ans. 5A)
106. What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series?
107. How can three resistors of resistances 2Ω, 3Ω and 6Ω be connected to give a total resistance of (a) 4Ω (b) 1Ω ?
108. Why does the cord of an electric heater not glow while the heating element does?
109. Compute the heat generated while transferring 96000 coulomb of charge in one hour through a potential difference of 50V. (Ans. 4800 kJ)
110. An electric iron of resistance 20 Ω takes a current of 5A. Calculate the heat developed in 30 s. (Ans. 15 kJ)
111. What determines the rate at which energy is delivered by current?
112. An electric motor takes 5A from a 220 V line. Determine the power of the motor and the energy consumed in 2 hours. (Ans. 1.1 kW, 2.2 kWh)
113. A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R’, then obtain the ratio of
114. An electric bulb is rated 220 V and 100 W. What will be the power consumed when it is operated on 110 V ? (Ans. 25 W)
115.
116.
V-I graph for parallel and series combination of two metallic resistors is shown as in figure 5. Which graph represents the parallel combination? Justify your answer.
117. Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then connected in parallel in a circuit across the same potential difference. Obtain the ratio of heat produced in series and parallel combination. (Ans. 1:4)
118. How many 176 Ω resistors in parallel are required to carry 5 A on a 220 V line? (Ans.4 resistors)
119. Several electric bulbs designed to be used on a 220 V electric supply line, are rated 10W. How many lamps can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A? (Ans. 110 bulbs)
120. Compare the power used in the 2Ω resistor in each of the following circuits:
(i) a 6 V battery in series with 1Ω and 2Ω resistors, and
(ii) a 6 V battery in parallel with 12 Ω and 2Ω resistors. (Ans. 8W, 18 W)
121. Which uses more energy, a 250 W TV set in 1 hour, or a 1200 W toaster in 10 minutes?
122. An electric heater of resistance 8Ω draws 15 A from the service mains for 2 hours. Calculate the rate at which heat is developed in the heater. (Ans. 1800 W)
123. (i) State the formula showing how the current I in a conductor varies when the potential difference V applied across it is increased stepwise.
(ii) Show this relationship on a schematic graph.
(iii) Calculate the resistance of a conductor if the current flowing it is 0.2 A, when the applied potential difference is 0.8V.
124. 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 4 hours. (Ans. 1.875 W, 3.3Ω, 0.0075kWh)
125. A wire of resistance 4Ω is doubled on it. Calculate the new resistance of the wire. (Ans. 1Ω)
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