Class 10 Science

# Magnetic Effect of Electric Current: Magnet

These notes are based on the chapter Magnetic Effect of Electric current class 10 science NCERT book and CBSE syllabus.

• Properties of magnet
• Magnetic field and field lines

A magnet is an object which produces magnetic field. The magnetic field is invisible and attracts ferro-magnetic materials such as iron, nickel and cobalt.

Magnets are naturally found in the form of rocks called magnetite. As per the folklore, magnets were first discovered in Magnesia. The discovery of magnet was accidental.

Apart from natural magnets, we can also make artificial magnets. Some artificial magnets are permanent while others are temporary. Magnets are used in many devices right from a simple stick on magnetic stickers to tiny magnets inside your earphone. Magnets are used in some of the highly complex devices such as MRI machines. MRI stands for Magnetic Resonance Imaging.

## Properties of Magnet

• A free suspended magnet always point towards north and south direction.
• The pole of a magnet which points toward north direction is called north pole or north seeking.
• The pole of a magnet which points toward south direction is called south pole or south seeking.
• Like poles of magnets repel each other while unlike poles of magnets attract each other.

## Magnetic field and Field Lines

The influence of force surrounding a magnet is called magnetic field. In the magnetic field, the force exerted by a magnet can be detected using a compass or any other magnet.

Fig: Magnetic Field Lines

The imaginary lines of magnetic field around a magnet are called field line or field line of magnet. When iron fillings are allowed to settle around a bar magnet, they get arranged in a pattern which mimicks the magnetic field lines. Field line of a magnet can also be detected using a compass. Magnetic field is a vector quantity, i.e. it has both direction and magnitude.

### Direction of Field Line

Outside the magnet, the direction of magnetic field line is taken from north pole to South Pole. Inside the magnet, the direction of magnetic field line is taken from south pole to north pole.

### Strength of magnetic field

The closeness of field lines shows the relative strength of magnetic field, i.e. closer lines show stronger magnetic field and vice-versa. Crowded field lines near the poles of magnet show more strength near the poles. Less crowded field lines appear between the poles showing less strength. As we move away from a magnet, field lines get sparser and sparser. This shows gradual reduction of magnetic field as we move far from a magnet.

It is observed that when a compass is brought near a current carrying conductor the needle of compass gets deflected because of flow of electricity. This shows that electric current produces a magnetic effect. This phenomenon is called electromagnetism. This lesson is more about magnetic effect of electric current than about magnets.

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