Magnetic Effects of Electric Current

 Class 10 Science MCQs

1. Magnetic effect of current was discovered by
(a) Oersted
(b) Faraday
(c) Bohr
(d) Ampere

Ans: a
Explanation:
(a) Oersted showed that electricity and magnetism were related phenomena.

2. Inside the magnet, the field lines moves
(a) from north to south
(b) from south the north
(c) away from south pole
(d) away from north pole

Ans: a
Explanation:
(a) Magnetic field inside the magnet moves from south to north pole.

3. Relative strength of magnetic field at a point in the space surrounding the magnet is shown by the
(a) length of magnet
(b) thickness of magnet
(c) degree of closeness of the field.
(d) resistance offered by the surroundings

Ans: a
Explanation:
(a) The force acting on the pole of another magnet by the crowded magnetic field lines is greater.

4. Which of the following statement is not correct about the magnetic field?
(a) Magnetic field lines form a continuous closed curve.
(b) Magnetic field line do not interest each other.
(c) Direction of tangent at any point on the magnetic field line curve gives the direction of magnetic field at that point.
(d) Outside the magnet, magnetic field lines go from South to North pole of the magnet.

Ans: d
Explanation:
(d) Outside the magnet, magnetic field line emerges from North-pole and moves towards south-pole.

5. By which instrument, the presence of magnetic field be determined?
(a) Magnetic Needle
(b) Ammeter
(c) Galvanometer
(d) Voltmeter

Ans: a
Explanation:
(a) With the help of magnetic field, one can find the presence of magnetic field in a region by observing its deflection.

6. The pattern of the magnetic field produced by the straight current carrying conducting wire is
(a) in the direction opposite to the current
(b) in the direction parallel to the wire
(c) circular around the wire
(d) in the same direction of current

Ans: a
Explanation:
(c) Magnetic field line around a current carrying straight conductor is represented by concentric circles.

7. The strength of magnetic field around a current carrying conductor is
(a) inversely proportional to the current but directly proportional to the square of the distance from wire.
(b) directly proportional to the current and inversely proportional to the distance from wire.
(c) directly proportional to the distance and inversely proportional to the current
(d) directly proportional to the current but inversely proportional the square of the distance from wire.

Ans: b
Explanation:
• magnetic field strength increases on increasing the current through the wire.
• magnetic field strength decreases as the distance from the wire increases.

8. A current through a horizontal power line flows from south to North direction. The direction of magnetic field line 0.5m above it is
(a) North
(b) South
(c) West
(d) East

Ans: a
Explanation:
(a) Apply right-hand thumb rule.

9. The nature of magnetic field line passing through the centre of current carrying circular loop is
(a) circular
(b) ellipse
(c) parabolic
(d) straight line

Ans: d
Explanation:
(d) magnetic field line at the centre of current carrying loop appears as a straight line.

10. The strength of each of magnet reduces to half when it cut along its length into the equal parts magnetic field strength of a solenoid. Polarity of solenoid can be determined by
(a) use of compass needle
(b) Right hand thumb rule
(c) fleming left hand rule
(d) either (a) or (b)

Ans: d
Explanation:
(d) both (a) and (b) can be use to determine the polarity of solenoid.

11. The factors on which one magnetic field strength produced by current carrying solenoids depends are
(a) Magnitude of current
(b) Number of turns
(c) Nature of core material
(d) All of the above

Ans: d
Explanation:
(d) Factors shown in (a), (b) and (c).

12. A soft iron bar is introduced inside the current carrying solenoid. The magnetic field inside the solenoid
(a) will decrease
(b) will remains same
(c) will increase
(d) will become zero

Ans: c
Explanation:
(c) Soft iron inside the current carrying solenoid act as an electromagnet.

13. When current is parallel to magnetic field, then force experience by the current carrying conductor placed in uniform magnetic field is
(a) Twice to that when angle is 60°
(b) Thrice to that when angle is 60°
(c) zero
(d) infinite

Ans: a
Explanation:
(a) If the current direction is parallel to the magnetic field, then there will no force on the conductor exerted by the magnetic field.

14. A positive charge is moving upwards in a magnetic field directed towards north. The particle will be deflected towards
(a) west
(b) north
(c) south
(d) east

Ans: a
Explanation:
(a) Apply fleming’s left hand rule

15. Which of the following factors affect the strength of force experience by a current carrying conduct in a uniform magnetic field?
(a) magnetic field strength
(b) magnitude of current in a conductor
(c) length of the conductor within magnetic field
(d) All of above.

Ans: d
Explanation:
(d) All the factors affect the strength of magnetic force.

16. Direction of rotation of a coil in electric motor is determined by
(a) fleming’s right hand rule
(b) fleming’s left hand rule
(c) faraday law of electromagnetic inductors
(d) None of above

Ans: b
Explanation:
(b) Fleming’s left hand rule.

17. In electric motor, to make the coil rotating continuously in the same direction, current is reversed in the coil after every half rotation by a device called
(a) carbon brush
(b) commutator
(c) slip ring
(d) armature

Ans: b
Explanation:
(b) A device that reverses the direction of current in the arms of armature through a circuit is called commutation.

18. The condition for the praenomen of electromagnetic induction is that there must be a relative motion between
(a) the galvanometer and magnet
(b) the coil of wire and galvanometer
(c) the coil of wire and magnet
(d) the magnet and galvanometer

Ans: c
Explanation:
(c) The relative motion between the magnet and coil of wire causes change in magnetic field lines linked with the coil to produces induced current if the circuit is closed.

19. The instrument that use to defect electric current in the circuit is known as
(a) electric motor
(b) A.C generator
(c) galvanometer
(d) none of the above

Ans: a
Explanation:
(a) A galvanometer is an instrument that can direct the presence of current in a circuit.

20. We can induce the current in a coil by
(a) moving the coil in a magnetic field
(b) by changing the magnetic field around it
(c) by changing the orientation of the coil in the magnetic field
(d) All of above

Ans: a
Explanation:
(a) The method can be used to induce the potential difference across the ends of a coil and hence induce current.

21. A magnet is moved towards a coil (i) quickly (ii) slowly. The induced potential difference
(a) more in (i) than in (ii) case
(b) more in (ii) than in (i) case
(c) same in both
(d) can’t say

Ans: a
Explanation:
(a) When magnet is moved quickly, more will be the changing magnetic field strength and hence larger is the induced potential difference.

22. A.C generator works on the principle of
(a) force experience by a conductor in magnetic field
(b) electromagnetic induction
(c) electrostatic
(d) force experience by a charge particle in electric field.

Ans: a
Explanation:
(a) Generator works on principle of electromagnetic induction.

23. Fleming’s left hand and Right hand rules are used in
(а) Generator and electric motor
(b) Electric motor and generator
(c) any rule can be used for any device
(d) both are not applied for generator and motor.

Ans: b
Explanation:
(b) Electric motor employs Fleming left hand rule while for generator, Fleming right-hand rule is used.

24. A D.C generator works on the principle of
(a) ohnis law
(b) Joule’s law of heating
(c) faraday’s law of electromagnetic induction.
(d) none of the above

Ans: c
Explanation:
(c) electric generator works on the basis of electromagnetic induction.

25. If the current values periodically from zero to a maximum value, back to zero and then reverses its direction, the current is
(a) direct
(b) alternative
(c) pulsating
(d) none of the above

Ans: b
Explanation:
(b) The alternating current reverse its direction periodically.

26. Earth wire carries
(a) current
(b) voltage
(c) no current
(d) heat

Ans: c
Explanation:
(c) Earth wire carries no current.

27. The main advantage of A.C power transmission over D.C power transmission over’ long distance is
(a) AC transmit without much loss of energy
(b) less insulation problem
(c) less problem of instability
(d) easy transformation.

Ans: a
Explanation:
(a) AC transmit over a long distance without much loss of energy as compare to DC.

28. Which among of these are the main characteristics of fuse element?
(a) High conductivity
(b) low melting point
(c) do not bum due to oxidation
(d) All of the above

Ans: d
Explanation:
(d) Fuse wire must have all the characteristic to prevent from a possible damage.

29. Overloading is due to
(a) Insulation of wire is damaged
(b) fault in the appliances
(c) accidental hike in supply voltage
(d) All of the above

Ans: d
Explanation:
(d) All are the causes to occur overloading

30. For a current in a long straight solenoid N-pole and S-pole are created at the two ends. Among the following statements, the incorrect statement is
(a) The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid.
(b) The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil.
(c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.
(d) The N-pole and S-pole exchange position when the direction of current through the solenoid is reversed.

Ans: c
Explanation:
(c) A solenoid behaves like a bar magnet. Hence the pattern of magnetic field associated with solenoid and around the bar magnet is same.

31. Commercial electric motors do not use
(a) an electromagnet to rotate the armature
(b) effectively large number of turns of conducting wire in the current carrying coil
(c) a permanent magnet to rotate the armature
(d) a soft iron core on which the coil is wound

Ans: c
Explanation:
(c) Using electromagnet, the magnetic field strength further increase by increasing the current. Hence it will enhance the power of electric.

32. The strength of magnetic field inside a long current carrying straight solenoid is
(a) more at the ends than at the centre
(b) minimum in the middle
(c) same at all points
(d) found to increase from one end to the other

Ans: c
Explanation:
(c) A current carrying solenoid produces a uniform magnetic field inside it.

33. To convert an AC generator into DC generator
(a) split-ring type commutator must be used
(b) slip rings and brushes must be used
(c) a stronger magnetic field has to be used
(d) a rectangular wire loop has to be used

Ans: a
Explanation:
(a) To connect AC generator into DC generator, split ring type commutation must be used to get a unidirectional direct current.

34. The most important safety method used for protecting home appliances from short circuiting or overloading is
(a) earthing
(b) use of fuse
(c) use of stabilizers
(d) use of electric meter

Ans: b
Explanation:
(b) It is most important method for protecting the electrical devices from short circuiting or overloading by stopping the flow of any large electric current exceeds from its rating.

35. What should be the core of an electromagnet?
(a) soft iron
(b) hard iron
(c) rusted iron
(d) none of above

Ans: a
Explanation: (a) soft iron

36. Who has stated the Right hand Thumb Rule?
(a) Orsted
(b) Fleming
(c) Einstein
(d) Maxwell

Ans: d
Explanation: (d) Maxwell

37. What is that instrument which can detect the presence of electric current in a circuit?
(a) galvanometer
(b) motor
(c) generator
(d) none of above

Ans: a
Explanation: (a) galvanometer

38. Which device produces the electric current?
(a) generator
(b) galvanometer
(c) ammeter
(d) motor

Ans: a
Explanation: (a) generator

39. The best material to make permanent magnets is
(a) aluminium
(b) soft iron
(c) copper
(d) alnico

Ans: d

40. The magnetic field lines always begin from
(a) N-pole and end on S-pole.
(b) S-pole and end on N-pole.
(c) start from the middle and end at N-pole.
(d) start from the middle and end at S-pole.

Ans: a

41. The magnetic field is the strongest at
(a) middle of the magnet.
(b) north pole.
(c) south pole.
(d) both poles.

Ans: d

42. Material of the core of a strong magnet is
(a) aluminium
(b) soft iron
(c) copper
(d) steel

Ans: b

43. Magnetic lines of force inside current carrying solenoid are
(a) perpendicular to axis.
(b) along the axis and are parallel to each other.
(c) parallel inside the solenoid and circular at the ends.
(d) circular.

Ans: c

44. A soft iron bar is introduced inside a current carrying solenoid. The magnetic field inside the solenoid
(a) will become zero.
(b) will increase.
(c) will decrease.
(d) will remain unaffected.

Ans: b

45. An electric generator actually acts as
(a) a source of electric charge.
(b) a source of neat energy.
(c) an electromagnet.
(d) a converter of energy.

Ans: d

46. A magnetic field directed in north direction acts on an electron moving in east direction. The magnetic force on the electron will act
(a) vertically upwards.
(b) towards east.
(c) vertically downwards.
(d) towards north.

Ans: c

47. The direction of force on a current carrying conductor in a magnetic field is given by
(a) Fleming’s left hand rule.
(b) Fleming’s right hand rule.
(c) Right hand thumb rule.
(d) Left hand thumb rule.

Ans: a

48. The direction of induced current is given by
(a) Fleming’s right hand rule.
(b) Fleming’s left hand rule.
(c) Right hand thumb rule.
(d) Left hand thumb rule.

Ans: a

49. Switches are connected to
(a) live wire.
(b) neutral wire.
(c) earth wire.
(d) any one.

Ans: a

50. The most important safety method used for protecting home appliances from short-circuiting or Overloading is
(a) earthing
(b) use of stabilizers
(c) use of fuse
(d) use of electric meter

Ans: c