Exploring Magnets Part 3: MCQs (Q51–Q75)
Part 3 — Questions 51–75 (Experiments, demonstrations, magnetic & non-magnetic substances, real-life uses)
51. In the classic experiment to show magnetic field lines, we sprinkle iron filings around a magnet on a sheet of paper. The role of the paper is to
A. Prevent filings from sticking to the magnet directly and show pattern clearly
B. Provide nutrients to filings
C. Turn filings into a permanent magnet
D. Generate electricity
Correct answer: A ← Correct answer: A
Explanations:
A) Correct — paper separates filings from the magnet and allows pattern visibility.
B/C/D) Not relevant.
52. Which of the following objects will a magnet pick up?
A. A wooden spoon
B. A steel pin ← Correct answer: B
C. A plastic toy
D. A glass bead
Explanations:
A/C/D) Non-magnetic materials.
B) Correct — steel (iron) is attracted by magnets.
53. How can you make a paper clip into a temporary magnet?
A. Heat it strongly only
B. Stroke it several times in same direction with a strong magnet ← Correct answer: B
C. Bend it into a circle only
D. Put it in sunlight for a long time
Explanations:
A/C/D) Ineffective or damaging.
B) Correct — stroking aligns tiny domains creating temporary magnetism.
54. Which instrument uses a magnet to determine direction?
A. Thermos flask
B. Compass ← Correct answer: B
C. Microscope
D. Magnifying glass
Explanations:
A/C/D) Not direction finders.
B) Correct — a compass uses magnetised needle.
55. Which of these is not a correct use of magnets?
A. Holding notes on a refrigerator door
B. Heating food in microwave directly using permanent magnets ← Correct answer: B
C. In electric motors and generators
D. In magnetic separators in industry
Explanations:
A/C/D) Valid magnet uses.
B) Incorrect — microwaves heat food via electromagnetic radiation, not by placing magnets inside.
56. A magnetic compass gets deflected if placed near a telephone because
A. Telephone tastes salty
B. Electronic devices and current-carrying wires produce magnetic fields that disturb compass ← Correct answer: B
C. Telephones sing and scare the needle
D. Compass melts near plastic
Explanations:
A/C/D) Incorrect.
B) Correct — local EM fields disturb compass.
57. Which of the following statements is TRUE?
A. All metals are magnetic
B. Only some metals (iron, nickel, cobalt) are strongly magnetic ← Correct answer: B
C. Wood is magnetic always
D. Water is attracted strongly to magnets
Explanations:
A/C/D) Incorrect.
B) Correct — ferromagnetic metals exhibit strong attraction.
58. A magnetic needle is balanced on a pivot. If the pivot is lubricated, the needle will
A. Not rotate at all
B. Rotate freely and align with the magnetic field more easily ← Correct answer: B
C. Turn into gold
D. Start to fly away
Explanations:
A/C/D) Wrong.
B) Correct — lubrication reduces friction allowing free alignment.
59. In a classroom demonstration, the teacher brings a magnet near a coil of wire and shows movement. This demonstrates the relationship between electricity and magnetism and is related to
A. Boyle’s law only
B. Electromagnetism (Oersted / Faraday principles) ← Correct answer: B
C. Theory of relativity only
D. Photosynthesis
Explanations:
A/C/D) Irrelevant.
B) Correct — current produces magnetism (Oersted) and changing magnetic fields induce current (Faraday).
60. Which part of the magnet is best for picking up a small steel pin stuck on a flat surface?
A. The middle of a long bar magnet
B. A small strong magnetised point or the pole area ← Correct answer: B
C. A wooden hammer
D. A cotton cloth
Explanations:
A) Middle has weaker field.
B) Correct — poles have strongest field, best for lifting small items.
C/D) Non-magnetic.
61. The magnetic effect of an electric current was discovered by
A. Newton
B. Oersted ← Correct answer: B
C. Fleming only
D. Darwin
Explanations:
A/C/D) Incorrect historical figures for this discovery.
B) Correct — Hans Christian Ørsted observed a compass deflect when near a current-carrying wire.
62. Which of the following can demagnetise a permanent magnet?
A. Storing it in a wooden box gently
B. Heating strongly or dropping/hitting the magnet ← Correct answer: B
C. Keeping it away from electrical currents always
D. Using it to pick up paper clips gently
Explanations:
A/C/D) Not likely to demagnetise.
B) Correct — heat and shock disturb alignment of magnetic domains causing loss.
63. Magnetic separators in industry are used to
A. Increase temperature of food
B. Separate magnetic impurities (iron) from non-magnetic material ← Correct answer: B
C. Make metal melt faster
D. Colour wood
Explanations:
A/C/D) Incorrect.
B) Correct — magnets remove iron/other magnetic particles from grains, ores etc.
64. Which arrangement of two bar magnets will give the strongest attraction?
A. North near North
B. South near South
C. North near South with poles close together ← Correct answer: C
D. Poles far apart and like poles facing
Explanations:
A/B/D) Weaker or repulsive depending.
C) Correct — opposite poles close give strong attraction.
65. Magnetic field lines inside a solenoid (long coil) are
A. Chaotic with no direction
B. Nearly uniform and parallel inside the coil ← Correct answer: B
C. Only outside the coil exist
D. Only present when wire is disconnected from current
Explanations:
A/C/D) Incorrect.
B) Correct — solenoid produces strong uniform field inside like a bar magnet when current flows.
66. The Earth’s magnetic field protects us by
A. Heating Earth’s core only
B. Deflecting charged particles from the Sun (solar wind) ← Correct answer: B
C. Making it rain always
D. Guiding birds only (not true)
Explanations:
A/C/D) Incorrect.
B) Correct — magnetosphere shields against solar wind and cosmic radiation.
67. If a magnet is suspended by a thread and rotated slowly, it will
A. Break into two pieces
B. Settle pointing along magnetic North–South when rotation stops ← Correct answer: B
C. Disappear
D. Turn into a compass permanently regardless
Explanations:
A/C/D) Incorrect.
B) Correct — behaves like a compass needle aligning with Earth’s field.
68. Which of the following is NOT an example of an electromagnet?
A. Crane lifting scrap metal at junkyard
B. Electric bell
C. Regular bar magnet stuck on fridge ← Correct answer: C
D. Solenoid in a relay switch
Explanations:
A/B/D) Electromagnets used in these devices (magnetism via current).
C) Correct — ordinary fridge magnet is a permanent magnet, not an electromagnet.
69. Magnetic compass needles point approximately North–South because
A. They are attracted to the Moon only
B. Earth acts like a giant magnet with a magnetic axis ← Correct answer: B
C. Needles have engines inside to move them
D. Needles follow wind direction only
Explanations:
A/C/D) Incorrect.
B) Correct — needle aligns with Earth’s magnetic field.
70. Which property distinguishes a permanent magnet from a temporary magnet?
A. Permanent magnets never attract anything
B. Permanent magnets retain magnetism longer; temporary magnets lose it when field removed ← Correct answer: B
C. Temporary magnets are not made of metal
D. Permanent magnets change colour always
Explanations:
A/C/D) Incorrect.
B) Correct — key difference is persistence of magnetism.
71. A coil of wire with current behaves like
A. A loudspeaker only
B. A magnet (electromagnet) ← Correct answer: B
C. A compass needle only
D. A thermometer
Explanations:
A/C/D) Not correct.
B) Correct — current in coil produces magnetic field.
72. Which of the following will show maximum deflection of a compass needle?
A. A weak magnet placed far away
B. A strong magnet kept very near the compass ← Correct answer: B
C. A wooden stick under the table
D. A sheet of paper near the compass
Explanations:
A/C/D) Not effective.
B) Correct — stronger and nearer sources produce larger deflection.
73. Why are magnets used in junkyard cranes to lift scrap iron?
A. Because magnets heat up scrap iron to melt it
B. Because they can pick up heavy iron easily and can be turned off (electromagnets) ← Correct answer: B
C. To make non-metallic items fly
D. To produce electricity only
Explanations:
A/C/D) Incorrect.
B) Correct — electromagnets allow easy control for lifting/releasing.
74. Where would magnetic field be zero?
A. At the pole of a magnet always
B. At points far away where contributions of nearby magnets cancel out ← Correct answer: B
C. Inside iron filings pile always
D. Inside the Sun only
Explanations:
A/C/D) Incorrect.
B) Correct — fields can cancel at certain locations producing net zero.
75. Magnets are widely used in MRI machines because
A. They are cheap and small only
B. Strong magnetic fields help align atomic nuclei; combined with radio waves produce body images ← Correct answer: B
C. They make noise to scare people
D. They cook food inside body
Explanations:
A/C/D) Incorrect.
B) Correct — MRI uses strong magnets for medical imaging (advanced topic but commonly known).