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 eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

Silicon steel used in lamination mainly reduces

  1. Hysteresis loss

  2. Eddy current losses

  3. Copper loss

  4. All of the above

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Silicon steel used in lamination mainly reducesHysteresis loss,Eddy current losses,Copper loss. In order to minimize the eddy currents more,magnetic core is laminated . The hysteresis coefficient of silicon steel is less, so hysteresis loss can be reduced. used mainly because of the following advantages: low hysteresis loss. low copper loss due to lower grain resistance.

Multiple choice eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

Eddy currents are produced in a metallic conductor when

  1. The magnetic flux linked with it changes

  2. It is placed in a changing magnetic field.

  3. It is placed in a magnetic field.

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

Eddy currents are produced when the magnetic flux passing through the metal object continuously changes. This may happen due to many reasons:
1) The object is placed in a region with changing magnetic field.
2) The object continuously moves in and out of the magnetic field region (may be uniform or non uniform).

Multiple choice eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

A magnet is dropped down an infinitely long vertical copper tube

  1. The magnet moves with continuously increasing velocity and ultimately acquires a constant terminal velocity

  2. The magnet moves with continuously decreasing velocity and ultimately comes to rest

  3. The magnet moves with continuously increasing velocity but constant acceleration

  4. The magnet moves with continuously increasing velocity and acceleration
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As the magnet falls through the copper tube, changing magnetic flux induces eddy currents in the tube. According to Lenz's law, these eddy currents oppose the motion of the magnet, creating an upward magnetic force. Eventually, this magnetic drag balances gravity, and the magnet falls at a constant terminal velocity.

Multiple choice eddy currents motional emf electromagnetic induction electromagnetic induction and alternating currents physics

The working of magnetic braking of trains is based on

  1. Steady current

  2. Eddy current

  3. Alternating current

  4. Pulsating current
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 It works the same as a disk eddy current brake, by inducing closed loops of eddy current in the conductive rail, which generate counter magnetic fields which oppose the motion of the train.

Multiple choice physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

Identify the methods by which a magnet can be demagnetized.

  1. Heating a magnet strongly

  2. Repeated hammering of the magnet

  3. Storing it aligned with the N-S direction

  4. None of these
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

Methods by which a magnet can be demagnetized can be given as mentioned below: 
$(1)$ Heating a magnet strongly
$(2)$ Hammering the magnet several times or repeated hammering
$(3)$ By passing an alternating current through the magnet
Hence, the correct options $(A)$ and $(B)$.

Multiple choice physics fun with magnets let's make a magnet making magnets making and handling magnets

When the north pole of a bar magnet picks up an iron nail which of the following are induced in the nail ?

  1. North poles

  2. South poles

  3. A north pole and south pole

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

As the attraction occurs only in between two unlike poles, thus north pole of magnet induces south pole in the nail and north at the other end.

Multiple choice physics fun with magnets let's make a magnet making magnets making and handling magnets

All magnetic materials lose their magnetic properties when:

  1. Dipped in water

  2. Dipped in oil

  3. Brought near a piece of iron

  4. Strongly heated
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Curie- Temperature:
The temperature at which any magnetic field material loses its magnetic property which is at a much higher temperature thus being strongly heated,
Magnets can be demagnetized.
Multiple choice physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

Which all things can be used to make a magnet?

  1. Iron nail

  2. Needle

  3. Blade

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

Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include iron, nickel, cobalt, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone.

Multiple choice physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

Which of the following process are used to make a magnet?

  1. Casting of magnetic material

  2. Pressing and sintering of magnetic material

  3. Extruding of magnetic material

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

Casting of a magnetic material, pressing and sintering of magnetic material and extruding of magnetic material are the processes used for making permanent magnets.

Multiple choice physics properties of a magnetic field let's make a magnet making magnets making and handling magnets

A substance consisting of a coil of wire with an iron core and is only magnetized when an electric current flows through it is called :

  1. Magnet

  2. Electromagnet

  3. Coil

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

The phenomenon of converting a substance into a magnet by flowing an electric current through a coil around it is known as electromagnetism and the magnet so formed is known as electromagnet.