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

How can the polarity of an electromagnet be changed?

  1. By changing the number of coils

  2. By changing the intensity of current

  3. By changing the direction of current

  4. By changing the length of the core

  5. -
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This is the correct answer. Polarity of an electromagnet can be changed by changing the direction of current.

Multiple choice

A current-carrying straight conductor is placed along West-East direction. What will be the direction of the force experienced by this conductor due to Earth’s magnetic field?

  1. It will be deflected in the direction of current.

  2. It will be deflected opposite to the direction of current.

  3. It will be deflected vertically downwards.

  4. It will be deflected vertically upwards.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The direction of Earth’s magnetic field is from geographical South to geographical North. According to Fleming’s left-hand rule, a current-carrying straight conductor placed along West-East direction will be deflected vertically upwards.

Fleming’s Left hand rulestates that if we  stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor. 

Multiple choice

In which of the following ionization processes has the magnetic behavior changed?
P. C2 → C2+ Q. O2 → O2+ R. N2 → N2+ S. F2 → F2-

  1. P and Q

  2. P and R

  3. Q and R

  4. Q and S

  5. R and S
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

O2 (16 e-) : σ1s2 σ*1s2 σ2s2 σ*2s2 σ2pz2 π2px2 π2py2 σ *2pz2; diamagnetic O2+ (15 e-) : σ1s2 σ*1s2 σ2s2 σ*2s2 σ2pz2 π2px2 π2py2 σ *2pz1; paramagnetic

N2 (14 e-) : σ1s2 σ*1s2 σ2s2 σ*2s2 σ2pz2 π2px2 π2py2; diamagnetic N2+ (13 e-) : σ1s2 σ*1s2 σ2s2 σ*2s2 σ2pz2 π2px2 π2py1; paramagnetic

Multiple choice

In case of any electric and magnetic field that was created by any given distribution of charges and currents Jefimenko's equations are the explicit solution to which law/equation?

  1. Nernst heat theorem

  2. Maxwell's equations

  3. Third law of thermodynamics

  4. Second law of thermodynamics

  5. Clayperon-Claussius equation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Maxwell's equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits.

Multiple choice

Consider the following statements:

  1. Steel can be used to make permanent magnets.
  2. Glass is a good conductor of electricity.

Which of the given statements is/are correct?

  1. Only 1

  2. Only 2

  3. Both 1and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Statement 1 is correct. Steel is used to make permanent magnets because steel is an alloy of iron, and iron is the basic material that can be used to make permanent magnets. Statement 2 is incorrect. Glass is a bad conductor of electricity.

Multiple choice

Consider the following statements:

  1. Permanent magnets can be damaged by excessive heating.
  2. Magnetic compass can be used by pilots and navigators to find directions.

Which of the given statements is/are correct?

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Solution 1 is correct. If magnets are excessively heated, they can lose their magnetism. So, permanent magnets can be damaged by excessive heating.Statement 2 is also correct. Magnetic compass (which always direct towards North direction) can be used by pilots and navigators to find the direction.

Multiple choice

Which of the following are not the uses of a magnetic compass? (1) To find direction (2) To find the direction of magnetic field (3) To increase the strength of current in a circuit (4) To test the polarity of a magnet (5) To magnetise a magnetic material

  1. Only (1) and (2)

  2. Only (2) and (4)

  3. Only (1) and (3)

  4. Only (3) and (5)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A magnetic compass is not used to increase the strength of current in a circuit and to magnetise a magnetic material because it is considered as a test magnet having feeble strength. All the others 1, 2 and 4 are applications of magnetic compass.

Multiple choice

Consider the following statements:

  1. MRI is not recommended for a person, who has pacemaker on his chest.
  2. Magnetic poles can exist individually.

Which of the given statements is/are correct?

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Statement 1 is correct. MRI (Magnetic Resonance Imaging) is not recommended for a person who has pacemaker on his chest. Statement 2 is incorrect. A magnet has a north and south poles and they always exist in pair.

Multiple choice

Which of the following statements is true regarding the sensitivity of Electron Spin Resonance (ESR)?

  1. ESR sensitivity increases with increasing temperature and decreasing magnetic field.

  2. ESR sensitivity increases with increasing temperature and increasing magnetic field.

  3. ESR sensitivity increases with decreasing temperature and increasing magnetic field.

  4. ESR sensitivity increases with decreasing temperature and decreasing magnetic field.

  5. The sensitivity does not depend on temperature and magnetic field.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This answer is correct as we can see from the expression n1/n2 = e(-2µH/kT) that sensitivity of the instrument is greatly enhanced by using a high magnetic field and lowering the temperature.

Multiple choice

The opposite poles of two magnets

  1. repel each other

  2. attract each other

  3. do not show any interaction

  4. move clockwise
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The opposite poles of two magnets attract each other as unlike charges or unlike poles attract each other.

Multiple choice

Why should magnets be stored safely?

  1. Magnets become weak if handled carelessly.

  2. Magnets are expensive.

  3. Magnets break easily.

  4. Magnets attract all substances.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Magnets should be stored safely because they become weak and lose their magnetism if handled carelessly.