Electricity and Magnetism MCQ question and answer with solution | Physics Gk MCQs

An insulator is a type of material that offers very high resistance to the flow of electric current.

In an insulator, the electrons are tightly bound to their atoms and are not free to move, making it extremely difficult for electric charge to pass through.

Examples of insulators include rubber, glass, wood, plastic, and mica — all of which prevent the conduction of electricity effectively.

In contrast, conductors (Option A) have very low resistance and allow electric current to pass easily.

A resistor (Option C) is a component specifically designed to offer a certain, fixed amount of resistance in an electrical circuit but not extremely high resistance.

A semiconductor (Option D) has resistance values between those of a conductor and an insulator and its conductivity can be controlled by doping or temperature.

Therefore, an element that offers high resistance to conduction is called an insulator.

Hence, the correct answer is Option B: insulator.

In the domain of Electricity and Magnetism, magnetic keepers are utilized to protect magnets from self-demagnetisation.

When a permanent magnet is exposed to external influences or stored over time without magnetic keepers, it may undergo self-demagnetisation, resulting in a reduction of its magnetic strength. This effect occurs due to various factors such as the alignment of magnetic domains within the magnet gradually becoming disordered.

Magnetic keepers, also known as magnetic shunts or armatures, are ferromagnetic materials (usually soft iron) attached to the poles of a magnet. They serve to complete the magnetic circuit and help maintain the alignment of magnetic domains within the magnet, thus preventing self-demagnetisation.

While magnets can also be affected by external factors like the Earth's magnetic field (Option A), the effect of other magnets (Option B), and demagnetisation due to heating (Option D), magnetic keepers specifically address the issue of self-demagnetisation.

Therefore, Option C: self-demagnetisation is the reason why magnetic keepers are used to protect magnets in the realm of Electricity and Magnetism.