Physics

Magnetism and Electromagnetism

1,011 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 physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Which of the following effects of current does not depend on the direction of current?

  1. Lighting and chemical effects

  2. Heating and lighting effects

  3. Heating and magnetic effects

  4. Magnetic and chemical effects
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Heating effect and lighting effect does not depend on the direction of current.

Multiple choice physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

What inferences were drawn from Oersteds experiment?

  1. A current or a moving charge produces magnetic field around it

  2. Presence of magnetic field can be detected using a compass needle

  3. The strength and direction of the magnetic field depends on the magnitude and direction of the current

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Oersted conducted an experiment to study the magnetic effect of electric current. In this experiment he observed the deflections of a compass needle placed in close proximity of an electric wire carrying current. He observed that in the absence of current the needle came to rest in Earths North-south direction under the influence of Earths magnetic field. However, when the needle was kept in close proximity of an electric wire carrying current it showed deflections in the east and west direction depending on the direction of current. Thus, indicating that the strength and direction of the magnetic field depends on the magnitude and direction of the current.

Multiple choice physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

The magnitude of current is ........ the magnitude of magnetic field

  1. Inversely proportional to

  2. Directly proportional to

  3. Same as

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In his experiment Oersted observed that as the current in the wire increased, the deflection of the needle also increased, indicating that they are directly proportional.

Multiple choice physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Which of the following observations are true for Hans Oersteds experiment?
a. When current passes through the wire the compass needle comes to rest in a direction along the Earths magnetic field.
b. When placed just above the wire, North Pole of the compass needle deflects towards the east when current is passes from A to B.
c. When placed just below the wire, North Pole of the compass needle deflects towards the east when current is passes from B to A i.e. on reversing the direction of current

  1. a and c

  2. a and b

  3. b and c

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Oersted conducted an experiment to study the magnetic effect of electric current. In this experiment he observed the deflections of a compass needle placed in close proximity of an electric wire carrying current. He observed that in the absence of current the needle came to rest in Earths North-south direction under the influence of Earths magnetic field. However, when the needle was kept below the wire and current was passed from A to B the north pole of the needle deflected towards the west and on reversing the direction of the current from B to A, it deflected towards the east. Similarly, when the needle was kept above the wire and current was passed from A to B the north pole of the needle deflected towards the east and on reversing the direction of the current from B to A, it deflected towards the west. This indicates that the direction of the magnetic field depends on the direction of current.

Multiple choice physics electromagnetic forces magnetic field due to a circular current carrying conductor magnetic field produced in a circular loop oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

State whether True or False :

If electric current is passed through metal body then it behaves as magnet.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If electric current is passed through metal body then it behaves as magnet. passing an electric current through iron does not produce a magnet. But if you pass a direct current through a coil wound around the piece of iron, you will magnetize it. Passing a direct electric current through the same coil with no iron inside the coil will still produce a magnetic field that behaves just like a magnet. Similarly, passing a direct current through a coil around a piece of Bismuth will create the same magnetic field which behaves just like a magnet.

Multiple choice motion of charged particle in magnetic field and electric field moving charges and magnetism magnetic effects of current and magnetism physics

Cathode rays are made to pass between the poles of a magnet. The effect  of magnetic field is 

  1. to increase their velocity

  2. to deflect them towards north pole

  3. to deflect them towards south pole

  4. to deflect them out of the plane of magnetic field
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When a magnetic field is  applied, the cathode ray is  deflected from its normal  straight path into a curved path which can be identified by right hand thumb rule.

Multiple choice motion of charged particle in magnetic field and electric field moving charges and magnetism magnetic effects of current and magnetism physics

A positive charge is released from the origin at a place where uniform electric field $E$ and a uniform magnetic field be exist along the positive $y-$axis and positive $z-$axis respectively, then :  

  1. initial the charge particle tends to move along positive $z-$axis
  2. initial the charge particle tends to move along negative $Y-$direction
  3. initial the charge particle tends to move along positive $y-$direction
  4. the charge particle moves in $y-z$ plane
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Lorentz force is F = q(E + v x B). Initially, the velocity v is zero, so the magnetic force is zero. The electric field E is along the positive y-axis, so the initial force F = qE is also along the positive y-axis, causing the particle to accelerate in that direction.

Multiple choice physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

Assertion : When diamagnetic material is placed in a non-uniform magnetic field, it tends to move from stronger to the weaker part of the magnetic field.
Reason : Diamagnetic materials possess strong magnetism.

  1. If both assertion and reason are true and reason is the correct explanation of assertion.

  2. If both assertion and reason are true and reason is not the correct explanation of assertion.

  3. If assertion is true but reason is false.

  4. If both assertion and reason are false.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Electrons is an atom orbiting around nucleus possess orbital angular momentum. These orbiting electrons are equivalent to current-carrying loop and thus possess orbital magnetic moment. Diamagnetic substances are the ones in which resultant magnetic moment in an atom is zero. When magnetic field is applied, those electrons having orbital magnetic moment in the same direction slow down and those in the opposite direction speed up. Thus, the substance develops a net magnetic moment in direction opposite to that of the applied field.

Multiple choice physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

Assertion : At high temperature, a ferromagnet becomes a paramagnet.
Reason : The ferromagnetic property depends on temperature.

  1. If both assertion and reason are true and reason is the correct explanation of assertion.

  2. If both assertion and reason are true and reason is not the correct explanation of assertion.

  3. If assertion is true but reason is false.

  4. If both assertion and reason are false.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At enough high temperature, a ferromagnet become a paramagnet. The domain structure disintegrates with temperature.

Multiple choice physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

If a magnetic material is having magnetic susceptibility $(\chi)=-1$, then the relative magnetic permeability $(\mu _r)$ and type of magnetic material is?

  1. $0$, diamagnetic
  2. $2$, ferromagnetic
  3. $1$, paramagnetic
  4. $-1$, diamagnetic
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Here, $\chi =-1$
then $\mu _r=1+\chi \Rightarrow \mu _r=1+(-1)=I-1=0$
Since, magnetic susceptibility of given material is less than one. Hence, the given magnetic material is a diamagnetic material.

Multiple choice physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

Which of the following is true regarding dimagnetic substances (symbols have their usual meaning)?

  1. ${ \mu } _{ r }>1,{ \chi } _{ m }>1$
  2. ${ \mu } _{ r }>1,{ \chi } _{ m }<1$
  3. ${ \mu } _{ r }<1,{ \chi } _{ m }<0$
  4. ${ \mu } _{ r }<1,{ \chi } _{ m }>0$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Diamagnetic substances induce magnetic field in the direction opposite to an external applied magnetic field and thus are repelled by external applied magnetic field.

Magnetic susceptibility of these substances is very small and negative    i.e    $\chi _m  < 0$ 
For example:
For silicon, $\chi _m =  -4.2 \times 10^{-6}$
From the equation, $\mu _r = 1+ \chi _m$
Thus, $\chi _m<0$ $\implies  \mu _r  <1$    
Hence, such materials have magnetic permeability less than unity.

Multiple choice physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

Susceptibility is large and positive for

  1. para magnetic

  2. diamagnetic

  3. ferro magnetic

  4. electromagnetic
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Diamagnetic          Paramagnetic             ferromagnetic
-1 $\leq$ $\chi$ < 0            0 < $\chi$ < $\varepsilon$                 $\chi$ >>1
$\chi $$=$magnetic susceptibility