Question

1.Explain how a solenoid works - how does it produce a magnetic field?

2. What are the five major types of magnetic materials? Describe each briefly.

Answer 1

1.An insulated copper coil is wound around some cylinderical cardboard. The length of coil is always greater than its diameter. When an electric current flows through it. It behaves like a magnet and it is called s solenoid.

If the current is in clockwise direction then the left hand side of each turn of the coil acts as south pole and right hand side acts as north pole.

If current is in anticlockwise direction then the left side acts as north lole and right side acts as south pole

Solenoid behaves like a bar magnet. So if the no. Of turns in the solenoid increases then magneti field also increases.

2. There are 5 types of magnetic materials.

A). Diamagnetism- It arises due to change in the orbital motion of electron in the presence of external magnetic field. It is generally found in those solids which have paired electrons in their atoms.

Examples- Copper, Aluminum, Germanium, Silicon

B). Paramagnetism- It is found in those solids which have permanent magnetic moment in their atoms. This permanent magnetic moment comes from unpaired electron spin

In the presence of external magnetic field this permanent magnetic moment align in the direction of applied magnetic field.

Example- Molecular oxygen, chromium oxide, platinum, crown glass.

C). Ferromagnetism- It is also associated with permanent magnetic moment in the atoms due to unpaired electron spin.

In ferromagnetic solid there is a non - zero magnetization even in the absence of applied magnetic field, which is known as spontaneous magnetization.

Examples - Nickel, iron, cobalt and their alloys

D). Anti ferromagnetic - It originates from anti parallel alignment of near by magnetic moment and there is no magnetization in anti - ferromagnetic.

Example - NiO, MnO, MnS

E). Ferromagnetism- It is similar to antiferromagnetism except magnetjc moment at A and B sides are unequal in magnitude (see pic).

Example - Ferrites, Fe3O4, Ba4Co2Fe36O60