Class 10 Science Chapter 12 Magnetic Effect of Electric Current

1. Which scientist discovered the relationship between electricity and magnetism?

(A) Isaac Newton

(B) Hans Christian Oersted

(D) James Clerk Maxwell

Answer

Answer: (B) Hans Christian Oersted

2. What happens when an electric current passes through a metallic wire?

(A) It produces heat only

(B) It produces a magnetic field

(D) It stops the flow of charge

Answer

Answer: (B) It produces a magnetic field

3. What was Oersted’s key observation in his experiment with a compass and current-carrying wire?

(A) The compass needle remained stationary

(B) The compass needle was deflected

(D) The current stopped flowing

Answer

Answer: (B) The compass needle was deflected

4. What is the unit of magnetic field strength named after Oersted?

(A) Tesla

(B) Gauss

(D) Weber

Answer

Answer: (C) Oersted

5. What is the significance of Oersted’s discovery?

(A) It proved that electric current does not affect magnetism

(B) It established a relationship between electricity and magnetism

(D) It showed that electric current produces sound

Answer

Answer: (B) It established a relationship between electricity and magnetism

6. Why does a compass needle get deflected when brought near a bar magnet?

(A) Due to gravitational force

(B) Due to electrostatic force

(D) Due to air resistance

Answer

Answer: (C) Due to the magnetic field of the bar magnet

7. What do the iron filings around a bar magnet represent?

(A) Electric field lines

(B) Magnetic field lines

(D) Sound waves

Answer

Answer: (B) Magnetic field lines

8. What is a magnetic field?

(A) The area around a magnet where magnetic force can be detected

(B) The space where sound waves travel

(D) The area around an electric circuit

Answer

Answer: (A) The area around a magnet where magnetic force can be detected

9. Which of the following is true about magnetic field lines?

(A) They start from the south pole and end at the north pole

(B) They cross each other at some points

(D) They spread randomly in all directions

Answer

Answer: (C) They form closed loops from the north pole to the south pole

10. What happens when iron filings are sprinkled around a bar magnet?

(A) They move randomly

(B) They align themselves along magnetic field lines

(D) They repel each other

Answer

Answer: (B) They align themselves along magnetic field lines

11. What is the direction of magnetic field lines outside a bar magnet?

(A) From south pole to north pole

(B) From north pole to south pole

(D) Parallel to the magnet

Answer

Answer: (B) From north pole to south pole

12. Why do two magnetic field lines never intersect each other?

(A) They have no physical existence

(B) They represent different magnetic forces

(D) They cancel each other’s effect

Answer

Answer: (C) If they intersect, the compass needle would point in two directions

13. How can we visualize magnetic field lines around a magnet?

(A) Using an ammeter

(B) Using a voltmeter

(D) Using a thermometer

Answer

Answer: (C) Using iron filings

14. What happens to the density of magnetic field lines as the strength of the magnetic field increases?

(A) It decreases

(B) It remains constant

(D) It disappears

Answer

Answer: (C) It increases

15. What is the shape of magnetic field lines around a straight current-carrying conductor?

(A) Straight lines

(B) Concentric circles

(D) Random patterns

Answer

Answer: (B) Concentric circles

16. What determines the pattern of the magnetic field around a current-carrying conductor?

(A) The shape of the conductor

(B) The type of material

(D) The color of the wire

Answer

Answer: (A) The shape of the conductor

17. In which direction does the compass needle deflect when current flows through a straight conductor placed above it?

(A) Parallel to the wire

(B) Towards the conductor

(D) Opposite to the current direction

Answer

Answer: (C) Perpendicular to the conductor

18. What happens when the direction of current in a straight conductor is reversed?

(A) The direction of the magnetic field remains unchanged

(B) The magnetic field disappears

(D) The conductor starts moving

Answer

Answer: (C) The direction of the magnetic field is reversed

19. How does the strength of the magnetic field around a current-carrying conductor change with distance?

(A) It remains constant

(B) It decreases as distance increases

(D) It does not depend on distance

Answer

Answer: (B) It decreases as distance increases

20. Which of the following factors affects the strength of the magnetic field produced by a current-carrying conductor?

(A) The type of conductor

(B) The amount of current flowing

(D) The shape of the battery

Answer

Answer: (B) The amount of current flowing

21. What happens to the magnetic field strength when the current in a conductor increases?

(A) It decreases

(B) It remains the same

(D) It disappears

Answer

Answer: (C) It increases

22. How does the magnetic field behave as the distance from a current-carrying conductor increases?

(A) It remains constant

(B) It decreases

(D) It reverses direction

Answer

Answer: (B) It decreases

23. What is the shape of the magnetic field around a straight current-carrying conductor?

(A) Straight lines

(B) Elliptical

(D) Random patterns

Answer

Answer: (C) Concentric circles

24. What is the right-hand thumb rule used for?

(A) Finding the direction of electric current

(B) Determining the shape of magnetic field lines

(D) Calculating resistance in a circuit

Answer

Answer: (C) Finding the direction of the magnetic field around a current-carrying conductor

25. According to the right-hand thumb rule, if the thumb points in the direction of current, how do the fingers curl?

(A) Randomly

(B) Straight

(D) Perpendicular to the conductor

Answer

Answer: (C) In concentric circles around the conductor

26. What does the right-hand thumb rule help to determine?

(A) The direction of electric current

(B) The direction of magnetic field around a current-carrying conductor

(D) The strength of the magnetic field

Answer

Answer: (B) The direction of magnetic field around a current-carrying conductor

27. If the current in a vertical conductor flows downward, what will be the direction of the magnetic field around it?

(A) Clockwise

(B) Counterclockwise

(D) Random

Answer

Answer: (A) Clockwise

28. What happens to the magnetic field lines as we move farther from a current-carrying conductor?

(A) They become closer

(B) They remain unchanged

(D) They become stronger

Answer

Answer: (C) They spread out

29. How does reversing the direction of current affect the magnetic field around a conductor?

(A) It has no effect

(B) It doubles the magnetic field strength

(D) It eliminates the magnetic field

Answer

Answer: (C) It reverses the direction of the magnetic field

30. Which of the following statements about magnetic field lines is true?

(A) They intersect each other

(B) They form closed loops

(D) They are strongest at the center of a conductor

Answer

Answer: (B) They form closed loops

31. What happens to the magnetic field when the number of turns in a current-carrying coil is increased?

(A) It remains the same

(B) It decreases

(D) It disappears

Answer

Answer: (C) It increases

32. Which of the following statements about magnetic field lines is correct?

(A) They start from the south pole and end at the north pole

(B) They intersect each other

(D) They spread randomly in all directions

Answer

Answer: (C) They always form closed loops

33. How does the magnetic field inside a solenoid behave?

(A) It is zero

(B) It increases as we move towards the ends

(D) It is uniform

Answer

Answer: (D) It is uniform

34. What happens to the magnetic field if the current through a straight conductor is increased?

(A) It remains constant

(B) It increases

(D) It reverses direction

Answer

Answer: (B) It increases

35. Which of the following best describes a solenoid?

(A) A coil of many circular turns of insulated copper wire

(B) A straight current-carrying wire

(D) A simple electric circuit

Answer

Answer: (A) A coil of many circular turns of insulated copper wire

36. What is the direction of the magnetic field inside a solenoid?

(A) From north to south

(B) From south to north

(D) Circular around the solenoid

Answer

Answer: (A) From north to south

37. Why is soft iron used as the core of an electromagnet?

(A) It increases resistance

(B) It retains magnetism permanently

(D) It blocks the electric current

Answer

Answer: (C) It enhances the magnetic field strength

38. Which factor affects the strength of the magnetic field inside a solenoid?

(A) The thickness of the wire

(B) The type of insulating material

(D) The shape of the solenoid

Answer

Answer: (C) The number of turns and current flowing through it

39. What happens if a soft iron core is placed inside a current-carrying solenoid?

(A) The magnetic field weakens

(B) The solenoid stops working

(D) The current decreases

Answer

Answer: (C) The magnetic field strengthens

40. Which statement about the magnetic field inside a solenoid is correct?

(A) It is strongest at the center

(B) It is weaker at the center

(D) It is absent inside

Answer

Answer: (A) It is strongest at the center

41. What is an electromagnet?

(A) A permanent magnet

(B) A magnet made by passing current through a coil

(D) A bar magnet

Answer

Answer: (B) A magnet made by passing current through a coil

42. What happens to an electromagnet when the current is switched off?

(A) It becomes stronger

(B) It loses its magnetism

(D) It heats up

Answer

Answer: (B) It loses its magnetism

43. Which of the following is NOT a use of an electromagnet?

(A) Electric bell

(B) Lifting heavy loads in scrapyards

(D) Generating hydroelectric power

Answer

Answer: (D) Generating hydroelectric power

44. Which material is commonly used as the core of an electromagnet?

(A) Copper

(B) Aluminium

(D) Plastic

Answer

Answer: (C) Soft iron

45. How can the strength of an electromagnet be increased?

(A) By reducing the number of turns in the coil

(B) By decreasing the current

(D) By using a plastic core

Answer

Answer: (C) By increasing the number of turns and current

46. What happens when a current-carrying conductor is placed in a magnetic field?

(A) It starts rotating

(B) It experiences a force

(D) It stops conducting electricity

Answer

Answer: (B) It experiences a force

47. Which scientist suggested that a magnet must exert an equal and opposite force on a current-carrying conductor?

(A) Isaac Newton

(B) Hans Christian Oersted

(D) Michael Faraday

Answer

Answer: (C) Andre-Marie Ampere

48. Which rule is used to determine the direction of force on a current-carrying conductor in a magnetic field?

(A) Right-hand thumb rule

(B) Fleming’s left-hand rule

(D) Kirchhoff’s law

Answer

Answer: (B) Fleming’s left-hand rule

49. What happens when the direction of current in a conductor is reversed while placed in a magnetic field?

(A) The direction of force remains the same

(B) The conductor disappears

(D) The conductor stops conducting

Answer

Answer: (C) The direction of force is reversed

50. In which direction does the force act on a conductor placed in a magnetic field?

(A) Parallel to the field

(B) Opposite to the current

(D) Randomly in any direction

Answer

Answer: (C) Perpendicular to both the field and current

51. Which rule helps determine the direction of motion of a conductor in a magnetic field?

(A) Ohm’s Law

(B) Fleming’s Left-Hand Rule

(D) Faraday’s Law

Answer

Answer: (B) Fleming’s Left-Hand Rule

52. According to Fleming’s Left-Hand Rule, what does the thumb represent?

(A) Direction of current

(B) Direction of magnetic field

(D) Magnitude of current

Answer

Answer: (C) Direction of force or motion

53. Which of the following devices works on the principle of force on a current-carrying conductor in a magnetic field?

(A) Electric motor

(B) Transformer

(D) Voltmeter

Answer

Answer: (A) Electric motor

54. What happens when the direction of the magnetic field is reversed in a current-carrying conductor?

(A) The conductor stops conducting

(B) The direction of the force on the conductor reverses

(D) The current flow increases

Answer

Answer: (B) The direction of the force on the conductor reverses

55. In Fleming’s Left-Hand Rule, what does the forefinger represent?

(A) Direction of current

(B) Direction of magnetic field

(D) Direction of resistance

Answer

Answer: (B) Direction of magnetic field

56. Which of the following devices works on the principle of Fleming’s Left-Hand Rule?

(A) Electric motor

(B) Transformer

(D) Resistor

Answer

Answer: (A) Electric motor

57. What is the role of a split-ring commutator in an electric motor?

(A) To increase resistance

(B) To reverse the direction of current in the coil

(D) To stop the motor

Answer

Answer: (B) To reverse the direction of current in the coil

58. Which of the following parts of an electric motor rotates?

(A) Stator

(B) Armature

(D) Battery

Answer

Answer: (B) Armature

59. Why does an electric motor continue to rotate in the same direction?

(A) Due to constant magnetic field

(B) Due to continuous current flow

(D) Due to friction

Answer

Answer: (C) Due to the commutator reversing the current

60. What happens if the current through an electric motor is stopped?

(A) It continues rotating

(B) It reverses direction

(D) It accelerates

Answer

Answer: (C) It stops rotating

61. What is the main function of an electric motor?

(A) To convert electrical energy into mechanical energy

(B) To convert mechanical energy into electrical energy

(D) To increase voltage

Answer

Answer: (A) To convert electrical energy into mechanical energy

62. Which part of an electric motor reverses the direction of current?

(A) Armature

(B) Battery

(D) Field magnet

Answer

Answer: (C) Split-ring commutator

63. Which force is responsible for the rotation of the coil in an electric motor?

(A) Electrostatic force

(B) Magnetic force

(D) Frictional force

Answer

Answer: (B) Magnetic force

64. What happens to the direction of rotation if the polarity of the battery in an electric motor is reversed?

(A) It remains the same

(B) It stops rotating

(D) It rotates faster

Answer

Answer: (C) It reverses direction

65. Which rule is used to determine the direction of force in an electric motor?

(A) Fleming’s Right-Hand Rule

(B) Fleming’s Left-Hand Rule

(D) Ohm’s Law

Answer

Answer: (B) Fleming’s Left-Hand Rule