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 uniform magnetic field lines of earth magnetism physics

To measure the magnetic moment of a bar magnet, one may use

  1. a deflection galvanometer if the earth's horizontal field is known

  2. an oscillation magnetometer if the earth's horizontal field is known

  3. both deflection and oscillation magnetometer if the earth's horizontal field is not known

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

If horizontal component of earth's magnetic field is known, one can use either deflection galvanometer or oscillation magnetometer.
If horizontal component of  earth's magnetic field is  not known, we will need two measurements for two variables $M$ and $B _H$

Multiple choice uniform magnetic field lines of earth magnetism physics

The length of a magnet is large compared to its width and breadth. The time period of its oscillation in a vibration magnetometer is $2 sec$. The magnet is cut along its length into $3$ equal parts and the $3$ parts are then placed on each other with their like poles together. The time period of this combination will be

  1. $2 sec$
  2. $\dfrac{2}{9}sec$
  3. $2\sqrt{3}sec$
  4. $\dfrac{2}{\sqrt{3}}sec$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$\dfrac{T _1}{T _2} =\sqrt{\frac{I _1}{I _2}} \sqrt{\dfrac{M _2}{M _1}}   ........(1)$
When the magnet is cut into three pieces, pole strength of the cut pieces is same as the original pole strength.
$I _1 =\dfrac{ml^2}{12}$
$I _2 = \dfrac{\dfrac{m}{3}(\dfrac{l}{3})^2}{12}$
$ \therefore = \dfrac{I _1}{I _2} = \dfrac{27}{1}$
$M _1 = pole \times l$ where pole is the pole strength.
$M _2= pole \times \dfrac{l}{3}$
$\dfrac{M _2}{M _1} = 3$
Eqn$(1)$  becomes
$\dfrac{T _1}{T _2}= \sqrt{\dfrac{27}{1}}\sqrt{3}=9$
Given $T _1=2$
$ \therefore T _2 = \dfrac{2}{9}$

Multiple choice physics electric current and its effects electric fuse electrical fuse and mcb fuse

Which one of the following statements is not correct?

  1. The two main organs of the human body where the magnetic field produced is quite significant are the heart and the brain.

  2. In a house circuit, lamps are used in parallel

  3. Switches,fuses and circuit breakers should be placed in the neutral wire

  4. A generator with commutator produces direct current
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Switches, fuses and circuit breakers must be placed in the live wire, not in neutral wire. And all the other statements given are correct.

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

Read the following statements carefully and pick out the correct choice of answer.
A: Susceptibility is expressed as ${ Am }^{ -1 }$.
B: Magnetic flux is expressed ${ JA }^{ -1 }$.

  1. A is correct but B is wrong.

  2. A is wrong but B is correct.

  3. Both A and B are wrong.

  4. Both A and B are correct.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Susceptibility is unit less.
Magnetic flux is expressed $Vs$ or $[M^1L^2T^{-2}A^{-1}] = JA^{-1}$.


Hence, option B is correct.

Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

A compass placed in an electric field will be deflected due to:

  1. heating effect of current

  2. magnetic effect of current

  3. conducting effect

  4. resistance of the needle to the electric field
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An electric current causes a magnetic field around it just like a magnet causes a magnetic field. When you moved the compass near an electric field, the magnetic field produced due to the electric field deflects the compass.


Hence, the correct option is $\text{B}$

Multiple choice

Magnetic poles are attracted to their....?

  1. Same Pole

  2. Opposite Pole

  3. Either Pole

  4. Own Magnet
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In magnetism, opposite poles attract each other (North attracts South), while like poles repel each other (North repels North, South repels South).

Multiple choice

What materials are attracted to magnets?

  1. Iron

  2. Copper

  3. Aluminum

  4. Wood
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Iron is a ferromagnetic material, meaning it is strongly attracted to magnets. Metals like copper and aluminum, as well as non-metals like wood, are not magnetic.

Multiple choice

Earth is a magnet?

  1. True

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

Earth acts as a giant magnet due to the movement of molten iron in its outer core, which generates a magnetic field. This is why compasses work.