I. Multiple Choice Questions.
1. SI unit of Electric current
A. Ampere (A) B. ohm (Ω)
C. Volt (V) D. Watt (W)
Ans: A. Ampere (A)
2. SI unit of Power
A. Ampere (A) B. ohm(Ω)
C. Volt (V) D. Watt (W)
Ans: D. Watt (W)
3. The property of the conductor that opposes the flow of charges through it is called
A. electric current
B. electric potential difference
C. electric resistance
D. electric power
Ans: C. Electric resistance
4. Rate of flow of electric charges called
A. Electric current B. Electric potential
C. Electric resistance D. Electric power
Ans: A. Electric current
5. The work done in bringing an unit charge from one point to another through conductor is called
A. electric current B. electric potential
C. electric resistance D. electric power
Ans: B. Electric potential difference
6. Rate of consumption of energy is called
A. electric current
B. electric potential difference
C. electric resistance
D. electric power
Ans: D. Electric power
7. The symbol used to represent Electric cell
A.
B.
C.
Ans: D
8. The symbol for closed circuit in electric circuit
A.
D.
Ans: A
9. The symbol used to represent dry cell in a circuit
A.
D.
10. Symbol in electric circuit represents
C. dry cell D. voltameter
Ans: a) resistor
11. In an electric circuit the ammeter and voltmeter are generally connected like this
A. both are connected in parallel
B. both are connected in series
C. ammeter in series & voltmeter in parallel
D. ammeter in parallel & voltmeter in series
Ans: c)ammeter in series &voltameter in parallel
12. Formula that is not applicable to represent ohm’s law is
A. V/I = R B. V = IR
C. I = V/R D. V = I/R
Ans: D. V = I/R
13. The net resistance when 2 Ω & 4 Ω resistors are connected in series and a 4 Ω resistor is connected in parallel is
A. 2Ω B. 2.4 Ω C. 4 Ω D. 10Ω
Ans: B. 2.4 Ω
14. 6 Ω the resistance of a conductor is 27Ω. If it is cut into three equal parts and connected in parallel, then its total resistance is
A. 6Ω B. 3 Ω C. 9 Ω D. 27Ω
Ans: B) 3 Ω
15. The net resistance when 2 Ω & 3 Ω resistors are connected in parallel and a 2 Ω resistor is connected in series
A. 3.2 Ω B. 2 Ω C. 3 Ω D. 1 Ω
Ans: A) 3.2 Ω
16. A piece of metallic wire of resistance R is cut into 3 equal parts. These parts are then connected in parallel. If the total resistance of this combination is Rl, then the value of R : Rl is
A. 1:3 B. 1:9 C. 9:1 D. 3:1
Ans: B) 9 : 1
17. An electric circuit of 6V potential difference does the work of 24J, then the amount of charges flown
A. 2 C B. 4 C C. 6 C D. 10 C
Ans: B) 4C
18. If 10C of charges flow through an electric circuit of 4V potential difference, then the amount of work done is
A. 10 J B. 20 J C. 40 J D. 30 J
Ans: C) 40 J
19. An electric lamp whose resistance is 30 Ω and a conductor of 6 Ω resistance are connected in series to 9V battery as shown in the figure. The total current flowing in the circuit is
A. 4 A B. 36 A C. 0.25 A D. 0.6 A
Ans: C. 0.25
20. In a conductor if the amount of electric current is 4A then the resistance is 12 Ω. If the resistance is doubled then the electric current would be
A. 2 A B. 3 A C. 4 A D. 8 A
Ans: A) 2 A
21. The resistance of a conductor of length 4l is 4 Ω, if the length becomes 2l then the resistance will be
A. 0.5 Ω B. 2 Ω C. 4 Ω D. 8 Ω
Ans: B) 2 Ω
22. Device used to measure the potential difference
A. Galvanometer B. Ammeter
C. Speedometer D. Voltmeter
Ans: A) Voltameter
23. The formula for electric power is
A. P=I R B. VI= P
C. P = VR D. VR =P
Ans: B) VI = P
24. The correct statement related to resistance is it is
A. directly proportional to potential difference but inversely proportional to current
B. inversely proportional to potential difference but directly proportional to current
C. inversely proportional to both potential difference and current
D. directly proportional to both potential difference and current
Ans: A) resistance directly proportional to potential difference but inversely proportional to current
25. The safety device used to avoid short circuit.
A. fuse B. switch
C. resistor D. transistor
Ans: A) fuse
26. The formula used to measure electric current
A. E=VIt B. E=Pt C. E=RCt D. E=Vt
Ans: B) E=Pt
27. A device used to change the resistance in the electric circuit is
A. Voltameter B. Ammeter
C. Galvanometer D. rheostat
Ans: D. Rheostat
28. ‘Ohm’ is the SI unit of
A. Electric Charge
B. Resistance
C. Electric Current
D. Electric Potential Difference
Ans: B. Resistance
29. The metal used in the filament of an electric bulb is
A. Manganese B. Tungsten
C. Nickel D. Chromium
Ans: B. Tungsten
30. The SI unit of electric potential difference is
A. Volt B. Ampere
C. Ohm D. Coulomb
Ans: A. Volt
31. The resistance of an electric heater coil is 110 Ω. Then electric current, that an electric heater draws from a 220 V source is,
A. 0.5 A B. 0.11 A C. 2 A D. 3 A
Ans: C. 2 A
32. A device that is connected in series in an electric circuit is
A. Voltmeter B. Bar Magnet
C. Turbine D. Ammeter
Ans: D. Ammeter
34.
35.
36.
37.
38.
39.
40.
41.
42.
33. Observe the following table :
The best conductor of electricity among these materials is
A. N B. M C. K D. L
Ans: B. M
34. The function of fuse in an electric circuit is that it
A. Reverses the direction of an electric current
B. Shows the direction of motion of the electric current
C. Measures the potential difference
D. Protects the electrical appliances
Ans: D. Protects the electrical appliances
35. The correct formula that shows the relationship between potential difference, electric current and resistance in an electric circuit is
A. I = V/ R B. I = VR
C. V = R I D. R = I V
Ans: D. R = 𝑉𝐼
36. The device used to measure the rate of current in a circuit is
A. Ammeter B. Voltmeter
C. Galvanometer D. Battery
Ans: A. Ammeter
37. The SI unit of resistivity is
A. ohm B. volt
C. watt D. ohm-metre.
Ans: D. ohm-metre
38. Ohm's law gives the relationship between
A. potential difference and electric charge
B. potential difference and resistance
C. electric current and potential difference
D. electric current and electric power
Ans: C. electric current and potential difference
39. In an electric circuit to get an equivalent resistance Rs four resistors of 2 Ω each are first connected in series. Later to get an equivalent resistance of Rp the same resistors are connected in parallel. Then the ratio of Rs /Rp is
A.16:1 B. 2:1 C. 4:1 D. 8:1
Ans: A.16:1
40. SI unit of electric charge is
A. Coulomb B. Ampere
C. Joule D. Volt
Ans: A. Coulomb
41. The rate of energy consumed in an electric circuit is, electric
(A) current
(B) potential difference
(C) resistance
(D) power
Ans: D. power
42. When three resistors of different resistance are connected in parallel, the quantity that remains the same in all the resistors is
(A) current
(B) potential Difference
(C) resistance
(D) resistivity
Ans: B. potential Difference
43. A correct statement related to the conductors X and Y given in the below figures is
(A) Since the cross section of the conductor X is less the flow of current is more in this conductor
(B) The cross section of conductor Y is more and hence resistance in it is more
(C) Since the cross section of the conductor X is small it has a low resistance
(D) The conductor Y has more cross section than the conductor X and hence the flow of current is more in it
Ans: D. The conductor Y has more cross section than the conductor X and hence the flow of current is more in it.
II. One-mark Questions:
44. Two connecting wires of same length and same diameter are made up of copper and iron. Among these two which is having more resistance? Give reason.
Ans: Iron because the resistivity of iron is more compared to copper.
45. Two students A and B conduct experiment connecting R1 and R2 resistors in series and parallel and plot the graph of V-I as below. Who has plotted the graph correctly?
46. How many joules does 1 unit (kWh) have?
Ans: 3.6 X 106 J
47. Define 1 ohm?
Ans: If the potential difference across the two ends is 1V & the current through it is 1A then the resistance is said to be 1Ω.
48. What is the meaning of 1 Ampere?
Flow of one coulomb of charge per second is 1 Ampere.
49. How many electrons does 1 coulomb (C) have?
6 x 1018 electrons
50. The potential difference between two points of connecting wire is 1 volt. Define the statement.
Means that when 1 Joule of work is done to move a charge of 1 coulomb from one point to another
51. Name the devices used to measure electric current and potential difference.
Electric current - Ammeter
potential difference- Voltameter
52. What is the resistance of a conductor?
It is the property of the conductor to resist the flow of charges through it.
53. When did the resistance of a conductor becomes 1 Ω?
If the potential difference is 1V & the current through it is 1A then the resistance becomes 1 Ω.
54. Why is the nitrogen or argon gas filled inside the electric bulb?
To prolong the life of filament.
55. Name the commercial unit of electricity.
Kilo watt per hour (kwh)
56. How is fuse connected in an electric circuit?
In series.
57. What are the uses of fuse in domestic electric circuit?
Fuse melts when excess of current flows through the circuit due to heating effect of electric current ensures the safety of electric devices.
58. Why are tungsten wires used in electric bulb?
Due to its high resistivity, it is used in electric bulb.
59. Write the symbols for the following terms in electric circuit.
i) A wire joint ii) electric bulb.
Ans:
60. Write the diagram of the symbol of resistors used in electric circuit.
Ans:
61. What is the SI unit of potential difference? Name the device used to measure the potential difference.
Volt (V), Voltameter
62. Suggest any two measures to avoid overloading in domestic circuits.
Ans:
• Live and neutral wires should not come into direct contact.
• Too many appliances should not be connected to a single socket.
• Should always use quality wires and good quality electrical appliances. (Any two):
63. What are the reasons for occurring overload in an electric circuit?
Ans:
• Accidental hike in the supply voltage
• Connecting too many appliances to a single socket
• When live wire and neutral wire come into direct contact. ( Any two )
64. Write the symbols of the following components used in an electric circuit.
i) Rheostat ii) Wires crossing without joining
Ans:
65. Write the symbols of the following components used in an electric circuit.
i) Electric cell ii) Voltameter
Ans:
66. Draw the symbol diagram of two electric cells connected in series in an electric circuit.
Ans:
67. Can an electric heater of 2kW capacity be connected to an electric circuit of 15A rating, 220V potential difference? Justify your answer.
Ans:
68. What happens if the fuse is connected to the neutral wire instead of connecting it to the live wire in the meter board of the house?
Ans:
69. When the number of turns of a current carrying circular loop is increased by ten times what change that occurs in the magnetic field of it?
Ans:
III. Two marks Questions:
70. What is electric circuit? Write the schematic diagram of an electric circuit comprising cell, electric bulb, ammeter & plug key.
71. In which of the below devices the electric energy is used maximum?
72. Which of the below electrical appliances consume more energy?
73. 2 Ω, 3 Ω & 4 Ω resistors are connected in parallel & then in series. In which connection does their total resistance will be less than their resistance?
74. 2 Ω and 4 Ω resistors are connected in parallel. If 6 Ω resistor is used in place of 4 Ω, find the difference of total resistance of two types of connections.
75. Resistivity of copper 1.63 x 10-8 Ωm & its cross section is 10.3 x 10-5cm3. Calculate the length of wire needed to make a coil of 10 Ω resistance.
76. Electrical resistivity of some substances at 200C is given below.
i) Among silver and copper which is the good conductor. Why?
ii) Which material is suitable for electrical heating. Why?
77. Explain the working principle of electric fuse.
78. Define electric resistance and resistivity. How are they interrelated?
79. Explain the working mechanism of an electric bulb.
80. In domestic electric circuit it is suitable to connect electrical devices in parallel. Mention two reasons for it.
81. State Joule’s law of heating. How fuse is connected in an electrical circuit. Mention the metal used in a filament of an electric bulb and the gas filled in the bulb.
82. A bulb is marked 220 V and 40 W. Calculate the current flowing through the bulb and it‘s resistance.
83. If an electrical fan consumes energy at a rate of 880W in voltage 220V, calculate the electric current and electric resistance.
84. The resistivity of manganese wire of length 1 m is 1·84 × 10-2 m at 20°C. If the diameter of the wire is 3 × 10-4 Ω m, what will be the resistance of the wire at that temperature?
85. The resistance of a metal wire of length 2 m is 28 Ω at 20°C. The cross-sectional area of the wire is 1.26 × 10⁻⁹ m².
(i) Calculate the resistivity of the metal.
(ii) Find the resistance of the same wire if its length is 3m.
86. Observe the given circuit:
Calculate the total resistance in the circuit and the total current flowing in the circuit.
87. Observe the diagram of below given electric circuit. Find the total resistance and the total current of the circuit.
88. An electric bulb with a resistance of 50 Ω is connected to 10 V battery in an electric circuit. Calculate the electric current flowing through the electric bulb and electric power of the bulb.
89. 1000 J of heat is produced each 2 seconds in a 5 Ω resistor. Find the potential difference across the resistor.
90. A wire of given material having length ‘l’ and area of cross section ‘A’ has a resistance of 4 Ω. Find the resistance of another wire of the same material having length ½ and area of cross-section ‘2A’.
91. Placing a fuse in domestic electric circuits is essential. Why? Explain.
IV. Three marks questions:
92. Find out amount of electric current flowing through below circuit.
93. The value of resistors R1, R2 & R3 are 5 Ω, 10 Ω & 30 Ω. If they are connected to dry cell of 12V potential difference. Calculate
i) Electric current flowing through each resistor
ii) Total electric current through circuit.
iii) Total resistance of entire circuit.
94. A Refrigerator of 400 Watt works 10 hrs daily; an electric fan of 80 Watt works 6 hrs daily and an electric bulb of 18 Watt glows 6 hrs daily. If the rate of per unit is 3 rupees, then what is the amount of electric bill the owner has to pay in the month of June?
95. A 350W bread toaster is used 6 hours a day. A 250W iron box is used 4 hours a day. If these appliances are used for 30 days, calculate the total cost if the rate is Rs. 4 for 1kWh.
96. An electric fan rated 50 W is used for 6 hours in a day. What is the cost of the energy it consumes for 30 days at Rs.4 per 1kWh?
97. Among iron, silver and nichrome which one is utilised inside an electric iron box which works on the heating effect of electric current. Justify your answer with 3 reasons.
98. A connecting wire of 20 Ω resistance is drawn to double its length. Calculate the resistance in new situation.
99. i) State ohm’s law.
ii) List the factors on which the resistance of conductor depends.
100. State Joule’s law of heating. Explain the working of electric filament bulb.
101. The resistors R1, R2 and R3 have the values 10 Ω, 20 Ω and 60 Ω respectively, which have been parallelly connected to a battery of 24 V in an electric circuit. Then calculate the following:
i) The current flowing through each resistor
ii) The total current in the circuit
iii) The total resistance of the circuit.
102. Resistance of a metal wire of length 2 m is 28 Ω at 20°C. If the diameter of the wire is 0.04 mm then what will be the resistivity of the metal at that temperature?
V. Four marks questions:
103. a) Name any two devices that work on the application of Joule’s law.
b) Why are the alloys like nichrome used in electrical heating devices?
104. a) A bread-toaster rated 350 W is used for 15 hours a day. An electric iron box rated 250 W is used for 5 hours a day. Calculate the cost of using these appliances for 30 days, if the cost of 1 kWh is Rs. 4.
b) In which method the resistors R1 and R2 could be connected so that the equivalent resistance of that electric circuit becomes low? What is the change in the value of current in the circuit by this type of connection?
105. An electric heater connected to a 220 V generator draws a current of 10 A. What is the power of the electric heater? If it is used for 8 hours a day, then calculate the total cost of using it for 30 days at Rs. 5.00 per 1 kWh.
VI. Answer the following questions. (5 Marks)
106. i) What is the meaning of the statement -The potential difference between two points is 1V?
ii) Name the device used to measure potential difference.
iii) What is resistance of a conductor?
iv) What is electric power?
v) Write three formulae used to find it.
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