Magnetism and Electromagnetism Theory:

Any substance having the property of being attracted by or attracting the magnet is known as magnetic material.

On the basis of magnetic properties all the materials may be classified into three classes

• Ferromagnetic material
• Paramagnetic material
• Dia-magnetic material

Ferro-magnetic material:

These are the materials which are strongly attracted by a magnet. Materials such as iron, steel, nickel, cobalt and some of their alloys are known as Ferro-magnetic materials. Their relative permeability is very high ranging from several hundred to thousands

Para-magnetic material:

The materials which are not strongly attracted by magnets. Materials such as aluminum, tin, platinum, magnesium, manganese etc are known as paramagnetic in nature. Their relative permeability is slightly higher than unity. These materials are slightly magnetized when placed in strong magnetic field and act in the direction of magnetic field

Diamagnetic material:

These magnetic materials are repelled by a magnet. Materials such as zinc, mercury, lead, sulpur, copper, silver etc are known as diamagnetic materials. Their relative permeability is slightly less than unity. These materials are slightly magnetized when placed in magnetic field and acts in opposite direction of the magnetic field

Paramagnetic and diamagnetic materials are termed as non-magnetic materials

Magnetic Field due to current carrying conductor:

When a conductor carries an electric current, a magnetic field is produced all along its length. This lines of force corms a concentric rings around the conductor. The direction of current and the direction of magnetic field are at right angles to each other. The magnitude of the magnetic field associated with a current carrying conductor depends upon the magnitude of current and its direction depends upon the direction of flow of current.

The direction of the lines of force (magnetic field) around a straight current carrying conductor can be determined by any one of the following methods:

Magnetic Field due to Circular Loop:

Magnetic Field due to Solenoid:

The current carrying wire wound spirally in the form of helix, about an axis is shown in fig is known as solenoid or coil. Magnetic field produced due to the current carrying solenoid is fairly uniform over a small region in the middle of the coil. It acts like a bar magnet having north and south poles.

Force of Current Carrying Conductors Lying in Magnetic Field

Force between two parallel carrying conductors:

When two parallel conductors carrying current in same direction, the lines of force encircle each of the conductor in same direction and the resultant field is an envelope acting like elastic band tend to pull the conductors together

When two parallel conductors carrying current in opposite directions, the lines of force encircle but not concentric either with another or with the conductors. The lines of force are crowded between the conductors tending to repel the conductor further.

Electrical Circuits vs Magnetic Circuits Analogy:

• As the path of an electric current is known as electric current, similarly the path of magnetic flux is known as magnetic circuit
• As an electric emf is necessary to cause the flow of current in an electrical circuit, similarly magneto motive force (mmf) is required to create the magnetic flux in the magnetic circuits
• As the current flowing in an electrical circuit depends upon the emf and resistance of the circuit, similarly the magnetic flux or number of lines of force produced in any magnetic circuit depends upon the mmf acting in the circuit and reluctance of the circuit
• Electric circuit resistance causes heat to generate resulting in the wastage of energy, there is no wastage of energy due to reluctance in magnetic circuits. This is the difference between electrical circuit and magnetic circuit