Magnetism and Electromagnetism MCQ Question and Answer

Answer.1. Magnetomotive force

Explanation

Magnetomotive force (symbol: F), which is often abbreviated to m.m.f., is the term used to describe the means by which magnetic flux is set up within a magnetic circuit. In all practical magnetic circuits, this is provided using a current-carrying winding (coil) and is the product of the current and the number of turns in the winding. Its Sl unit of measurement is the ampere-turns and its CGS unit is G (Gilbert).

Answer.3. Spin of nucleus

Explanation:-

Materials are divided into two groups, that is, those with a permanent magnetic dipole and those without a permanent magnetic dipole. In the case of a permanent magnetic dipole, atoms themselves have magnetic moments even if there is no magnetic field (it is easy to understand that each of the atoms is a small magnet). Each of the electrons that spin around the nucleus has a magnetic moment, and magnetic properties exhibited by transition metal elements and rare earth metallic elements are induced by the orbital motion of electrons that spin around nuclei and the magnetic moments of the electrons themselves (electrons are magnets of the smallest size).

Answer.1. Placing it inside a coil carrying current

Explanation

A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called a solenoid. The field lines around a current-carrying solenoid are similar to that produced by a bar magnet. This means that a current-carrying solenoid behaves as a magnet having a north pole and a south pole. The strong magnetic field produced inside a solenoid can be used to magnetize a piece of a magnetic material like soft iron when placed inside the coil.

Answer.3. Same at all points

Explanation:-

Magnetic field lines are straight and parallel inside the solenoid. This indicates a magnetic field. Hence, inside the solenoid, the magnetic field is the same throughout.

Answer.3. 25 AT/m

Explanation:-

Magnetic field Strength

H = NI/l

Where,

N = number of truns = 50

I = Current = 1

L = Length = 200 mm = 200 × 10⁻³ m

Answer.1. Zero

Explanation:-

The force on a length L of the wire is given by

F = BIL sinθ

where θ is the angle between the current and the direction of the magnetic field. In parallel plate capacitor θ = 0.

F = BIL sin0°

F = 0

Answer.1. Tesla

Explanation

The unit of magnetic flux density or magnetic field induction is Tesla.

Answer.1. Soft iron

Explanation:-

Temporary magnets:-  Iron or soft steel will retain magnetism so long as the magnetizing force is applied. Once the magnetizing force is removed, they will lose nearly all their magnetism. Magnets made from such materials are called temporary magnets. They are used where temporary magnetism is required.

Answer.4. Two magnetic lines of  force do not cut each other

Explanation:-

The space surrounding a bar magnet/magnetic needle, in which its influence in the form of magnetic force can be detected, is called the magnetic field.

The curved lines around a bar magnet/magnetic needle, along which a freely suspended north pole will move in a magnetic field, is called the magnetic line of force or field line of force.

Characteristics of magnetic field lines.

• Magnetic lines of force are continuous and will always form closed loops. They are closed continuous curves, which originate from the north pole and end at south-pole, outside the bar magnet. Within the magnet, they run from south to north
• Magnetic lines of force will never cross one another. Two magnets placed near each other have separate magnetic fields which occupy an area common to both. One might gather from this that the lines of force cross or intersect. But this does not happen; lines of force never cross. When like poles face each other, the lines of force of each field remain separate entities, but -each field becomes distorted. When unlike poles face each other, the lines of force of each field interact with the other and produce a strong resultant field.
• Parallel magnetic lines of force traveling the same direction repel one another. Parallel magnetic lines of force traveling in opposite directions tend to unite with each other and form into single lines traveling in a direction determined by the magnetic poles creating the lines of force.
• Magnetic line of force never intersect each other:- Two lines of force never intersect each other, they did so, there would have been two tangents at the point of the intersection, that is two directions of the magnetic field at one point which is not possible
•  Magnetic lines of force pass through all materials, both magnetic and nonmagnetic. There is no known insulator for magnetic lines of force. It has been found that flux lines will pass through all materials. Thus, most material all, except for magnetic materials, has no effect on magnetic fields. Conductors, insulators, air, or even vacuum do not affect magnetic fields. However, they will go through some materials more easily Ban others. This fact makes it possible to concentrate flux lines where they are used, or to bypass them around an area or instrument.
• Magnetic lines of force tend to shorten themselves. Another important behavior of magnetic lines of force is that each magnetic line behaves as though it were a stretched rubber band which, if given the opportunity, would contract. This explains why unlike poles attract each other. The lines of magnetic force passing through the magnet behave as though they shrink, thus pulling the magnets towards each other.

Answer.2. Iron part

Explanation:-

The level of magnetic flux established in a ferromagnetic core is a direct function of the permeability of the material. Ferromagnetic materials have a very high level of permeability, while nonmagnetic materials such as air, vacuum, and would have very low levels of permeability.