⚡ UNIT – 11 : ELECTRICITY(Question)

 

⚡ UNIT – 11 : ELECTRICITY

---

I. Multiple Choice Questions (1 mark each)

1. The SI unit of electric current is
    A) Ampere B) Ohm C) Volt D) Watt

2. The SI unit of power is
    A) Ampere B) Ohm C) Volt D) Watt

3. The property of a conductor that opposes the flow of charges is called
    A) Electric current B) Potential difference C) Resistance D) Power

4. The rate of flow of electric charge through a conductor is
    A) Electric current B) Electric potential C) Electric resistance D) Electric energy

5. The work done in bringing a unit positive charge from one point to another is called
    A) Electric potential difference B) Current C) Resistance D) Power

6. The rate of consumption of electrical energy in a circuit is called
    A) Electric power B) Electric energy C) Current D) Resistance

7. The symbol of an electric cell is

8. The symbol of a closed circuit is

9. The symbol representing a dry cell is

10. The given symbol represents
     A) Resistor B) Ammeter C) Dry cell D) Voltmeter

11. In an electric circuit, the ammeter and voltmeter are connected as
     A) Both in series B) Both in parallel C) Ammeter in series and voltmeter in parallel D) Ammeter in parallel and voltmeter in series

12. The formula not representing Ohm’s Law is
     A) V = IR B) I = V/R C) R = V/I D) V = I/R

13. Two resistors of 2 Ω and 4 Ω are connected in series and another 4 Ω resistor in parallel with the combination. The total resistance is
     A) 2 Ω B) 2.4 Ω C) 4 Ω D) 10 Ω

14. A wire of 27 Ω resistance is cut into 3 equal parts and connected in parallel. The total resistance is
     A) 6 Ω B) 3 Ω C) 9 Ω D) 27 Ω

15. Two resistors of 2 Ω and 3 Ω are connected in parallel and another 2 Ω in series. The net resistance is
     A) 3.2 Ω B) 2 Ω C) 3 Ω D) 1 Ω

16. A wire of resistance R is cut into 3 equal parts and connected in parallel. The ratio of original to new resistance is
     A) 1 : 9 B) 9 : 1 C) 3 : 1 D) 1 : 3

17. The charge that flows when 2 A current passes for 2 seconds is
     A) 1 C B) 4 C C) 2 C D) 0.5 C

18. The work done in moving a 2 C charge through a potential difference of 20 V is
     A) 2 J B) 10 J C) 40 J D) 400 J

19. The resistance of a conductor through which 2 A current flows under 0.5 V potential difference is
     A) 0.5 Ω B) 1 Ω C) 0.25 Ω D) 2 Ω

20. The current through a 10 Ω resistor when 20 V potential difference is applied is
     A) 2 A B) 1 A C) 0.5 A D) 5 A

21. The equivalent resistance of two 4 Ω resistors connected in parallel is
     A) 8 Ω B) 2 Ω C) 4 Ω D) 16 Ω

22. The device used to measure potential difference is
     A) Voltmeter B) Ammeter C) Galvanometer D) Rheostat

23. The correct formula for electric power is
     A) P = I × R B) P = V × I C) P = V/R D) P = R × I²

24. Resistance is
     A) Directly proportional to potential difference and inversely proportional to current B) Inversely proportional to both C) Directly proportional to both D) None

25. The safety device used to avoid short-circuiting in a household circuit is
     A) Fuse B) Switch C) Resistor D) MCB

26. The formula to calculate electrical energy is
     A) E = VIt B) E = Pt C) E = I²Rt D) All of these

27. The device used to vary resistance in a circuit is
     A) Voltmeter B) Rheostat C) Ammeter D) Switch

28. Ohm is the SI unit of
     A) Electric potential difference B) Resistance C) Electric current D) Electric charge

29. The metal used for the filament of an electric bulb is
     A) Tungsten B) Aluminium C) Copper D) Iron

30. The SI unit of potential difference is
     A) Volt B) Ohm C) Joule D) Coulomb

---

II. One Mark Questions

31. Define electric current.

32. Define potential difference.

33. Define one ampere.

34. Define one volt.

35. State Ohm’s law.

36. Define resistance of a conductor.

37. What is a circuit diagram?

38. What are good conductors and insulators? Give examples.

39. Define one coulomb of charge.

40. Name the device used to measure electric current.

41. Name the device used to measure potential difference.

42. Write the relation between current, voltage and resistance.

43. Define one watt of power.

44. What is meant by electric power?

45. What is the commercial unit of electric energy?

46. How many joules are there in one kilowatt-hour?

47. State the law of combination of resistances in series.

48. State the law of combination of resistances in parallel.

49. Why are copper wires used in electric circuits?

50. What is an electric fuse?

51. Why is tungsten used for making bulb filaments?

52. What are the causes of overloading in household circuits?

53. Suggest two methods to prevent overloading.

54. Name the device used to regulate current in a circuit.

55. How are fuses connected in a circuit — series or parallel?

56. Write the symbols for (i) electric cell (ii) battery.

57. Write the symbols for (i) voltmeter (ii) ammeter.

58. Write the symbols for (i) rheostat (ii) resistor.

59. How are resistors connected to get (a) more resistance (b) less resistance?

60. Define electric power and write its SI unit.

---

III. Two Mark Questions

61. State and explain Ohm’s law.

62. Derive the relation between resistance, potential difference and current.

63. Write two factors on which resistance of a conductor depends.

64. State Joule’s law of heating and write its mathematical form.

65. Explain the heating effect of electric current with an example.

66. Explain how an electric fuse works in a circuit.

67. Derive the expression for equivalent resistance in (a) series and (b) parallel combinations.

68. Explain the meaning of electric power and write its three formulae.

69. Calculate the resistance of a wire if 0.5 A current flows through it under a potential difference of 3 V.

70. A bulb of 100 W is used for 10 hours. Find the electrical energy consumed in kWh.

⚡ UNIT – 11 : ELECTRICITY – KEY ANSWERS

---

I. Multiple Choice Questions (1 mark each)

Q.No	Correct Answer	Explanation
1	✅ A. Ampere	SI unit of current
2	✅ D. Watt	SI unit of power
3	✅ C. Electric resistance	Opposition to current
4	✅ A. Electric current	Rate of flow of charge
5	✅ B. Electric potential	Work done per unit charge
6	✅ A. Electric power	Energy consumed per second
7	✅ Symbol of a cell	One long and one short line
8	✅ Closed circuit	Continuous loop with switch ON
9	✅ Symbol of dry cell	Two parallel lines, one longer
10	✅ A. Resistor	Zig-zag symbol
11	✅ C. Ammeter in series, voltmeter in parallel	For correct readings
12	✅ D. V = I/R	Not correct form
13	✅ B. 2.4 Ω	Series + parallel calculation
14	✅ B. 3 Ω	$R_{eq} = R/9 = 27/9 = 3Ω$
15	✅ A. 3.2 Ω	Parallel 1.2 + series 2 = 3.2Ω
16	✅ B. 9:1	Resistance reduced nine times in parallel
17	✅ B. 4 C	$Q = I \times t = 2 \times 2 = 4C$
18	✅ C. 40 J	$W = QV = 2 \times 20 = 40J$
19	✅ B. 0.25 Ω	$R = V/I = 0.5/2 = 0.25Ω$
20	✅ A. 2 A	$I = V/R = 20/10 = 2A$
21	✅ B. 2 Ω	$R_{eq} = (4×4)/(4+4) = 2Ω$
22	✅ A. Voltmeter	Measures potential difference
23	✅ B. P = V × I	Power formula
24	✅ A. ∝ V and 1/I	Ohm’s law relation
25	✅ A. Fuse	Prevents excess current
26	✅ D. All of these	E = VIt = I²Rt = V²t/R
27	✅ B. Rheostat	Variable resistor
28	✅ B. Resistance	Unit of resistance is ohm
29	✅ A. Tungsten	High melting point
30	✅ A. Volt	SI unit of potential difference

---

II. One Mark Questions – Key Answers

31. Electric current: Rate of flow of charges.
     $I = \frac{Q}{t}$

32. Potential difference: Work done per unit charge.
     $V = \frac{W}{Q}$

33. 1 Ampere: Current when 1 coulomb charge passes in 1 second.

34. 1 Volt: Potential difference when 1 joule of work is done to move 1 coulomb.

35. Ohm’s Law: $V ∝ I$ or $V = IR$.

36. Resistance: Property opposing current flow.
     $R = V/I$.

37. Circuit diagram: Schematic showing electric components using symbols.

38. Good conductors: Allow current (e.g., copper).
     Insulators: Do not (e.g., plastic).

39. 1 Coulomb: Charge passing in 1 second when 1 A current flows.

40. Ammeter: Measures current in circuit.

41. Voltmeter: Measures potential difference.

42. Relation: $V = IR$.

43. 1 Watt: Power when 1 joule of work is done in 1 second.

44. Electric power: Rate of doing electrical work.
     $P = VI$.

45. Commercial unit: Kilowatt-hour (kWh).

46. 1 kWh = 3.6 × 10⁶ J.

47. Series law: $R = R₁ + R₂ + R₃ + …$.

48. Parallel law: $1/R = 1/R₁ + 1/R₂ + 1/R₃ + …$.

49. Copper wires: Low resistance, high conductivity.

50. Fuse: Safety device preventing overcurrent.

51. Tungsten: High melting point, doesn’t oxidize.

52. Overloading: Too many appliances or faulty wires.

53. Prevent: Use proper rating fuse, avoid overuse.

54. Rheostat: Used to vary current in circuit.

55. Fuse connection: In series with live wire.

56. Symbols:
     (i) Cell — long & short line. (ii) Battery — multiple cells.

57. Symbols:
     (i) Voltmeter — circle with V. (ii) Ammeter — circle with A.

58. Symbols:
     (i) Rheostat — rectangle with arrow. (ii) Resistor — zig-zag line.

59. More resistance: Series connection.
     Less resistance: Parallel connection.

60. Electric power: Rate of energy consumption; unit = Watt.

---

III. Two Mark Questions – Key Answers

61. Ohm’s Law:
    At constant temperature, $I ∝ V$
    or $V = IR$.

62. Relation derivation:
    From Ohm’s law, $R = V/I$.

63. Factors affecting resistance:
     (i) Length of conductor (∝ L)
     (ii) Area of cross-section (∝ 1/A)
     (iii) Material
     (iv) Temperature

64. Joule’s Law of Heating:
    Heat (H) ∝ I², R, and t
     Formula: $H = I²Rt$.

65. Heating effect:
    When current flows, energy dissipated as heat (e.g., heater, bulb).

66. Fuse working:
    Fuse melts and breaks circuit when current exceeds limit.

67. Equivalent resistance:

• Series: $R = R₁ + R₂ + R₃$

• Parallel: $1/R = 1/R₁ + 1/R₂ + 1/R₃$

68. Electric power:
    $P = VI = I²R = V²/R$.

69. Given: V = 3V, I = 0.5A
    $R = V/I = 3/0.5 = 6Ω$.

70. Given: 100 W, 10 hrs
    Energy = 100 × 10 ÷ 1000 = 1 kWh.