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

Non-metals contain magnetic material.

  1. True

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

Non-metals do not possess magnetic properties; magnetism is a characteristic associated with certain metals like iron, nickel, and cobalt.

Multiple choice

An electric lamp glows due to

  1. heating effect

  2. magnetic effect

  3. chemical effect

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

An electric lamp (incandescent bulb) glows because the filament resists the flow of electrons, causing it to heat up to a very high temperature and emit light.

Multiple choice

An electric current can produce

  1. heating effect

  2. chemical effect

  3. magnetic effect

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

Electric current can produce heat (like in a heater), chemical changes (like in electrolysis), and magnetic fields (like in an electromagnet).

Multiple choice mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

In mutual induction 
A: when current in one coil increases, induced current in neighbouring coil flows in the opposite direction
B: When current in one coil decreases, induced current in neighbouring coil flows in the opposite direction

  1. A is true, B is false

  2. A and B are false

  3. A and B are true

  4. A is false, B is true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Lenz's Law states that the induced current will flow in a direction that opposes the change in magnetic flux. If current in the primary coil increases, the induced current in the secondary coil creates a magnetic field opposing the increase (opposite direction). If current decreases, the induced current creates a field to support the flux (same direction). Thus, A is true and B is false.

Multiple choice mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

A cylindrical magnet is kept along the axis of a circular coil. On rotating the magnet about its axis. the coil will have induced in it

  1. No current

  2. A current

  3. Only an e.m.f.

  4. Both an e.m.f. and a current
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Rotating a cylindrical magnet about its own axis does not change the magnetic flux linked with the stationary circular coil. According to Faraday's law, no flux change means no induced EMF and no induced current.

Multiple choice mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

Identify which of the following best describe the Mutual inductance?

  1. the ability of a current carrying conductor to induce a voltage in another conductor through a mutual magnetic field.

  2. the ability of current carrying conductor to produce a changing magnetic field.

  3. the ability of a conductor to induce a magnetic field in another current carrying conductor.

  4. the ability of a current carrying conductor to induce a current in another conductor through a mutual magnetic field.

  5. the ability of a magnetic field to induce a voltage in a current carrying conductor.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As per the Faraday's experiments, a current in a conductor produces a magnetic field. This magnetic field gets linked with another conductor and result in an induced emf.

Multiple choice biology transport in mammals regulation of the activity of heart drug, tobacco and alcohol consumption community health and hygiene

Berger waves are produced by

  1. Magnet (7 Tesla)

  2. P.E.T. scan

  3. Brain

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

Berger waves, also called as $\alpha$-waves are neural oscillations in the frequency range of 7.5-12.5 Hz. $\alpha$-waves are called as Berger waves in the memory of the founder of EEG.
$\alpha$-waves are one type of brain waves detected either by either EEG, electroenccephalography or magnetoencephalography (MEG) and predominantly originate form the occipital lobe during wakeful relaxation with closed eyes.
Thus, the correct answer is option (C), 'Brain'.

Multiple choice biology transport in mammals regulation of the activity of heart drug, tobacco and alcohol consumption community health and hygiene

MEG is

  1. Magnetoencephalography

  2. Magnetoelectron transport

  3. Metallic emission tantrum

  4. Mixed electronic tachycardia
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Magnetoencephalography (MEG) is a non-invasive neurophysiological technique that measures the magnetic fields generated by neuronal activity of the brain. The spatial distributions of the magnetic fields are analyzed to localize the sources of the activity within the brain, and the locations of the sources are superimposed on anatomical images, such as MRI, to provide information about both the structure and function of the brain. 

Multiple choice biology transport in mammals regulation of the activity of heart drug, tobacco and alcohol consumption community health and hygiene

The weaker magnetic fields of the brain are studied with the help of 

  1. Electro cardiography

  2. SQUID

  3. Prosthesis

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

A SQUID (superconducting quantum interference device) is a very sensitive magnetometer used to measure extremely subtle magnetic fields, based on superconducting loops containing Josephson junctions. SQUIDs are sensitive enough to measure fields as low as 5 aT (51018 T) within a few days of averaged measurements. Magnetoencephalography (MEG), uses measurements from an array of SQUIDs to make inferences about neural activity inside brains. Because SQUIDs can operate at acquisition rates much higher than the highest temporal frequency of interest in the signals emitted by the brain (kHz), MEG achieves good temporal resolution.

Multiple choice physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

Read the following statements.
I. A magnetic field is unable to penetrate into a superconductor.
II. An electric field can be cut off by a screen of conducting material
III. Gravitational field can be freely transmitted through all bodies
Which statement is false?

  1. III

  2. II

  3. I

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

A. stronout feels weightless inside an artificial satellite because nothing is stopping their fall due to force of gravity.

Multiple choice physics magnetic effects of electric current electric generator ac generator effects of electric current

The laws of electromagnetic induction have been used in the construction of a :

  1. galvanometer

  2. voltmeter

  3. electric motor

  4. electric generator
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The laws of electromagnetic induction has been used in the construction of a electric generator. In electric generator, emf is induced by changing the flux.
Galvanometer is used to detect current. So, no use of electromagnetic induction.
Voltmeter is used to measure voltage. Again, no use of electromagnetic induction.
Electric motor changes electrical energy into mechanical energy, which has no use of laws of electromagnetic induction.

Multiple choice physics magnetic effects of electric current electric generator ac generator effects of electric current

A D.C. generator is based on the principle of.

  1. magnetic effect ofcurrent

  2. lighting effect ofcurrent

  3. electrochemical induction

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

Answer is D.

Electromagnetic induction is a process where a conductor placed in a changing magnetic field (or a conductor moving through a stationary magnetic field) causes the production of a voltage across the conductor. This process of electromagnetic induction, in turn, causes an electrical current - it is said to induce the current.
Hence, the D.C. generator is based on the principle of electromagnetic induction.

Multiple choice physics magnetism and electromagnetism electric generator ac generator magnetic effects of electric current

Carbon brushes are not necessary in a dynamo, if the coil remains stationary and the magnet moves, because

  1. Current is drawn from a stationary source

  2. Current is drawn from a moving source

  3. Direct current is produced

  4. It is not necessary to reverse the direction of the current.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Carbon brushes are not necessary in a dynamo, if the coil remains stationary and the magnet moves, because It is not necessary to reverse the direction of the current.The brushes transfer the electricity from outside the motor to the spinning winding in the center of the motor. They undergo quite a lot of friction, and after a while wear out. Carbon is used as it is a reasonable conductor, and is soft enough to wear down instead of wearing down the "comutator" - the ring the brushes press against. Brushes are designed to be replaceable in large motors because of this.