## Activity

1. Take a straight wire AB and pierced it through a horizontal cardboard such that wire AB is vertical.
2.   The ends of the wire AB are connected to a battery.
3.   Place some iron fillings on the cardboard.
4.   Switched the key on.
5.   Gently tap the cardboard.
6.   The iron fillings arrange themselves in concentric circles around the wire.
7.   This shows that magnetic field lines are concentric circles. The circles become larger and larger as we move away from the wire.

## Direction of field lines- Right Hand thumb rule

The direction of field lines due to a current carrying wire can be determined by using Right Hand Thumb Rule (Or Right Hand Grip Rule).

Imagine that you are holding a current carrying wire in your right hand such that the thumb is stretched along the direction of the current, then, the fingers will wrap around the conductor in the direction of the field lines of the magnetic field.

## Factors on which the magnetic field at a distance from the straight wire depends on

1.   Directly proportional to the current flowing in the wire.
2.   Inversely proportional to the distance from the wire.

## Others topics in this chapter:

4.   Solenoid

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