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.

Electromagnet coresMagnetic flux densityMagnetic lines of forceElectromagnetic inductionBar magnet propertiesMagnetic materials

Magnetism and Electromagnetism Questions

Multiple choice

Two bars are identical in size and shape, out of which one is a magnet. Which of the following is the correct way to distinguish between the two?

  1. Magnetic bar is hollow and hence, light weight.

  2. Magnetic bar will be heavy.

  3. Magnetic bar will show a deflection when someone touches it.

  4. Magnetic bar will attract an iron nail when taken near it.

  5. Magnetic bar will repel a plastic nail when taken near it.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Yes, magnet attracts all magnetic materials.

Multiple choice

A subwoofer is a loudspeaker designed to reproduce extremely low audio frequencies.The barium compound used in subwoofer magnets to provide power is

  1. barium azide

  2. barium bromide

  3. barium chloride

  4. barium ferrite
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Barium ferrite, BaFe2O4 and related ferrite materials are components of magnetic stripe cards.The Fe3+ centers, with a high-spin d5 configuration, are ferromagnetically coupled. This area of technology is usually considered to be an application of the related fields of materials science and solid state chemistry. It is also used in subwoofer magnets to provide power.

Multiple choice

Name the moving armature of dynamo.

  1. Rotor

  2. Slator

  3. Electric magnet

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

In a dynamo or electric motor, the rotating part is called the rotor (or armature). 'Slator' appears to be a misspelling of stator (the stationary part), electric magnet refers to electromagnets, and split ring is part of the commutator assembly.

Multiple choice

What type of magnetic material is normally used in bubble memories?

  1. Magnetic core

  2. Cobalt

  3. Garnet

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

Bubble memory technology uses thin films of garnet (typically garnet ferrite) as the magnetic material. These garnet films have magnetic domains that can form stable 'bubbles' representing data bits. Magnetic cores are used in core memory, cobalt has some applications but garnet is the standard for bubble memories, and metallic materials are not suitable for bubble formation.

Multiple choice

When a piece of soft iron is placed inside a current carrying solenoid, the magnetic field of the electromagnet produced

  1. disappears in a few seconds

  2. disappears when the current is turned off

  3. never disappears

  4. disappears when the current is increased

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

Yes, it is correct. The magnet formed by producing a magnetic field inside a solenoid is called an electromagnet, but when the current is turned off, the magnetic field disappears.

Multiple choice

Which of the following is incorrect regarding a solenoid?

  1. Solenoid has many turns

  2. The wire used in solenoid is of insulated aluminium wire

  3. Solenoid resembles the shape of a cylinder

  4. Magnetic materials can be magnetised inside it

  5. It has two ends North and South pole
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is the correct answer.