Physics

Magnetism and Electromagnetism

1,019 Questions

This hub provides practice questions on magnetism and electromagnetism. It covers magnetic flux density, electromagnets, magnetic lines of force, and electromagnetic induction. These physics concepts frequently appear in technical and non-technical competitive exams.

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Magnetism and Electromagnetism Questions

Multiple choice

New research has provided evidence supporting the theory of earth's magnetic field going haywire over the Bermuda Triangle that caused the disappearance of many airplanes and ships in the area.

  1. supporting the theory of earth's magnetic field going haywire over the Bermuda Triangle that caused

  2. supporting the theory that earth's magnetic field going haywire over Bermuda Triangle caused

  3. that supports the theory of earth's magnetic field going haywire over Bermuda Triangle that caused

  4. supporting the theory of earth's magnetic field going haywire over the Bermuda Triangle and causing
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Correct. The option removes the errors of misplaced modifiers.

Multiple choice

Diamagnetism is shown by _________.

  1. O22-

  2. O2+

  3. O2

  4. NO

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Correct option. This species has 18 electrons, which are filled in such a way that all molecular orbitals are fully filled, so diamagnetic.

Multiple choice

Which of the following is responsible for definite shape of an iron ball?

  1. Strong forces of attraction between molecules of iron ball

  2. Large distance between the molecules of iron ball

  3. High speed of molecules of iron ball

  4. Random motion of molecules of iron ball
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Iron ball is a solid, and its specific shape is because of strong forces of attraction between its molecules.

Multiple choice

When current is switched on through a wire, why does a magnetic compass needle kept nearby get deflected?

  1. Because of the movement of electric current

  2. Because of the electric field created around the wire

  3. Because of the magnetic field around the wire

  4. Because of the heating effect of the electric current

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When electric current passes through a conducting wire, a magnetic field is created around the wire. The magnetic field causes deflection in the magnetic compass needle.

Multiple choice

If in a circuit, electric current flows in a clockwise direction, will the compass needle deflect? If yes, then in which direction?

  1. No, the needle will not deflect.

  2. Yes, the needle will deflect in clockwise direction.

  3. Yes, the needle will deflect in anticlockwise direction.

  4. Yes, the needle will deflect in clockwise direction and then, come back to its original position.

  5. Yes, the needle will deflect in anticlockwise direction and then, come back to its original position.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Yes, it is correct. The deflection of the needle depends upon the flow of current. When the current flows clockwise, the compass needle deflects clockwise.

Multiple choice

Which of the following forms an electromagnet?

  1. Iron nail coiled with insulated copper wire

  2. Iron nail kept near a copper coiled wire

  3. Iron nail coiled with insulated copper wire, through which current is flowing

  4. Iron nail kept near a copper coiled wire, through which current is flowing

  5. Iron nail kept near a natural magnet
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Yes, it is correct. A magnetic material when placed between a current carrying coil, behaves like a magnet. 

Multiple choice

The magnetic material between a current-carrying coil

  1. becomes a permanent magnet

  2. is a magnet till the time current passes through it

  3. loses its magnetic property to some extent and gets weak

  4. changes its shape and acquires magnetic properties

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Yes, it is correct. The iron nail between the current-carrying coil is a magnet till it is in the magnetic field of electric current. This shows the magnetic effect of current.

Multiple choice

If A is a stronger electromagnet than B, then

  1. number of turns in the current-carrying coil around A > B

  2. strength of current in the coil around A > B

  3. the metal inside has more magnetic property in A

  4. Both 1 and 2

  5. 1, 2 and 3
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

All the three options are correct.

Multiple choice

__________ substances are those which can be magnetized to a great extent.

  1. Ferromagnetic

  2. Diamagnetic

  3. Paramagnetic

  4. Both (1) and (2)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ferromagnetic materials like iron, nickel, and cobalt can be magnetized very strongly because their atomic magnetic moments align parallel to each other, creating a strong net magnetic field. Diamagnetic materials are weakly repelled by magnetic fields and cannot be permanently magnetized. Paramagnetic materials are weakly attracted but much less so than ferromagnetic ones. Option D is incorrect because diamagnetic materials cannot be magnetized to any significant extent.

Multiple choice

As proposed in the passage, when does magnetic reversal take place?

Directions: Read the following passage and answer the question that follows.

Nothing is sure, but death and taxes, and of course, north is north and south is south, and thus, it has always been so. But, this is what they say, and there is no guarantee that it is the truth. You can believe that death and taxes are for real, but you might want to reconsider the part about south is south and north is north because many times during the history of our planet, north has become south and south has become north. This may sound extraordinarily fictitious, but it is true and a process called magnetic reversal is behind it. 
Paleogeologists have found that this phenomenon is the real thing, in a field study known as paleomagnetism, by investigating rocks. There is a lot that goes on before anything can be deciphered from the rocks. When rocks are being formed from magma, atoms within their crystals respond to Earth’s magnetic field by pointing towards the magnetic North pole of Earth. The magnetic force of attraction is generated by the North Pole on the atoms of rocks. By age dating the rocks and their magnetic alignment, scientists can determine where on Earth the North Pole was located at the time because as the rocks solidified, they trapped information within them. The study of ancient lava flows has shown that at certain periods in Earth’s history, magnetic north was located exactly at the place it is located at the moment.

It has now been determined that this reversal takes place quite regularly, i.e. every 500,000 years. The last reversal is said to have taken place approximately 700,000 years ago. The name given by scientists to the periods “normal” polarity is the magnetic orientation of the era. On the other hand, “reversed” polarity or the magnetic orientation of the reverse situation is called “magnetic chrons”.

Although, the fact of such reversal is clear, the answers to the how and why questions are debatable. Because no one precisely knows how Earth’s magnetic field is produced, it becomes difficult to say how it might be reversed. Among explanations proposed, is a reversal of direction of convection currents in the liquid outer core of the Earth or the collision between Earth and a meteorite or a comet. While the precise effects of reversal are not known, there can be little doubt that Earth would receive a great deal more damaging ultraviolet radiation during the process than it does now. There has also been correlation between such occurrences and the extinction of certain species of animals in the past.  

  1. After every 700,000 years

  2. After every 600,000 years

  3. Nothing can be said

  4. Around every 500,000 years

  5. After an earthquake
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

It is mentioned in the passage 'quite regularly'. This indicates that it happens approximately every 500,000 years.

Multiple choice

According to the passage, what is the effect of magnetic reversal?

Directions: Read the following passage and answer the question that follows.

Nothing is sure, but death and taxes, and of course, north is north and south is south, and thus, it has always been so. But, this is what they say, and there is no guarantee that it is the truth. You can believe that death and taxes are for real, but you might want to reconsider the part about south is south and north is north because many times during the history of our planet, north has become south and south has become north. This may sound extraordinarily fictitious, but it is true and a process called magnetic reversal is behind it. 
Paleogeologists have found that this phenomenon is the real thing, in a field study known as paleomagnetism, by investigating rocks. There is a lot that goes on before anything can be deciphered from the rocks. When rocks are being formed from magma, atoms within their crystals respond to Earth’s magnetic field by pointing towards the magnetic North pole of Earth. The magnetic force of attraction is generated by the North Pole on the atoms of rocks. By age dating the rocks and their magnetic alignment, scientists can determine where on Earth the North Pole was located at the time because as the rocks solidified, they trapped information within them. The study of ancient lava flows has shown that at certain periods in Earth’s history, magnetic north was located exactly at the place it is located at the moment.

It has now been determined that this reversal takes place quite regularly, i.e. every 500,000 years. The last reversal is said to have taken place approximately 700,000 years ago. The name given by scientists to the periods “normal” polarity is the magnetic orientation of the era. On the other hand, “reversed” polarity or the magnetic orientation of the reverse situation is called “magnetic chrons”.

Although, the fact of such reversal is clear, the answers to the how and why questions are debatable. Because no one precisely knows how Earth’s magnetic field is produced, it becomes difficult to say how it might be reversed. Among explanations proposed, is a reversal of direction of convection currents in the liquid outer core of the Earth or the collision between Earth and a meteorite or a comet. While the precise effects of reversal are not known, there can be little doubt that Earth would receive a great deal more damaging ultraviolet radiation during the process than it does now. There has also been correlation between such occurrences and the extinction of certain species of animals in the past.  

  1. Formation of rocks

  2. Change in direction of convention currents

  3. The end of life of some species on Earth

  4. South becoming north and north becoming south

  5. Flow of lava out of the volcanoes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This can be deduced from the last line of the passage.

Multiple choice

'Magnetic north was directly opposite to its present location'. How can this be verified?

Directions: Read the following passage and answer the question that follows.

Nothing is sure, but death and taxes, and of course, north is north and south is south, and thus, it has always been so. But, this is what they say, and there is no guarantee that it is the truth. You can believe that death and taxes are for real, but you might want to reconsider the part about south is south and north is north because many times during the history of our planet, north has become south and south has become north. This may sound extraordinarily fictitious, but it is true and a process called magnetic reversal is behind it. 
Paleogeologists have found that this phenomenon is the real thing, in a field study known as paleomagnetism, by investigating rocks. There is a lot that goes on before anything can be deciphered from the rocks. When rocks are being formed from magma, atoms within their crystals respond to Earth’s magnetic field by pointing towards the magnetic North pole of Earth. The magnetic force of attraction is generated by the North Pole on the atoms of rocks. By age dating the rocks and their magnetic alignment, scientists can determine where on Earth the North Pole was located at the time because as the rocks solidified, they trapped information within them. The study of ancient lava flows has shown that at certain periods in Earth’s history, magnetic north was located exactly at the place it is located at the moment.

It has now been determined that this reversal takes place quite regularly, i.e. every 500,000 years. The last reversal is said to have taken place approximately 700,000 years ago. The name given by scientists to the periods “normal” polarity is the magnetic orientation of the era. On the other hand, “reversed” polarity or the magnetic orientation of the reverse situation is called “magnetic chrons”.

Although, the fact of such reversal is clear, the answers to the how and why questions are debatable. Because no one precisely knows how Earth’s magnetic field is produced, it becomes difficult to say how it might be reversed. Among explanations proposed, is a reversal of direction of convection currents in the liquid outer core of the Earth or the collision between Earth and a meteorite or a comet. While the precise effects of reversal are not known, there can be little doubt that Earth would receive a great deal more damaging ultraviolet radiation during the process than it does now. There has also been correlation between such occurrences and the extinction of certain species of animals in the past.  

  1. From the study of celestial bodies like comets and meteorites

  2. From the study of different types of rocks

  3. From the study of formation of rocks

  4. From the study of structure of rocks
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The passage explains that when rocks form from magma, 'atoms within their crystals respond to Earth's magnetic field by pointing towards the magnetic North pole' and as 'the rocks solidified, they trapped information within them.' Scientists determine where the North Pole was by 'age dating the rocks and their magnetic alignment.' This involves examining the internal structure of rocks (crystals and atomic alignment). Option D 'study of structure of rocks' best captures this process of examining trapped information in rock formations. Options A, B, and C are less precise or don't fully capture the structural analysis involved.