# Magnetic effects of Electric Current

#### Introduction:

Download full pdf notes of this chapter : Magnetic Effects of Electric Current

First of all a Danish Physicist Hans Christian Oersted found the magnetic effect of electric current. During an experiment, accidentally he found that a compass needle placed nearby of a current carrying metallic wire, got deflected. He performed a lot of experiments after that and showed that electricity and magnetism were related phenomena.

## Magnetic Field and  Magnetic Field lines:

We are familiar with the name magnet and we know that a magnet is a material which attracts iron particles. We are also familiar with compass needle ( in fact, a small bar magnet) and we know that if it is left freely to rotate then the end which point towards North  is considered to be the north pole of the needle( or bar magnet) and the end which point towards South  is considered to be south pole of the magnet.

The region or space around a magnet upto which the force of attraction can be experienced by any iron particle towards this magnet is known as its magnetic field. Magnetic field is a vector quantity.

If we place a bar magnet on a board and then sprinkle some iron fillings ( small iron particles) around it and then disturb the position of these iron filling continuously by tapping the board. We observe that these iron fillings arrange themselves in a specific manner under the influence of the magnetic field of the bar magnet.

The lines or curves around the bar magnet along which these iron filings arrange themselves is known as magnetic field lines

### Magnetic field lines are closed curves:

Outside the magnet, the magnetic field lines emerge from the North Pole and merge at the South pole and inside the magnet, the direction of field lines are from the South Pole to its North Pole. Hence these field lines make closed curves.

### Properties of magnetic field lines:

1. Magnetic field lines are closed curves.

2. Tangent to the curve of field lines at any point gives the direction of the magnetic field at that point.

3. No two field lines can cross each other.

## Magnetic field due to a Current Carrying Conductor:

A current carrying wire produces a magnetic field around it. The field lines of the magnetic field due to a current carrying straight conducting wire can be considered in the form of concentric circles as shown in figure.

The strength of this magnetic field decreases as one goes away from the wire, that is magnetic field due to the current carrying conducting wire decreases with the increase in distance from the wire.

### Right hand thumb rule :

Right hand thumb rule is a way to find the direction of magnetic field due to a current carrying a straight conductor.

• If we hold the current carrying a straight conductor with our right hand in such a way that our thumb points towards the direction of current. Then the fingers will wrap around the conductor in the direction of field lines of the magnetic field. This is called the right hand thumb rule.

Note's next topics :