Electric Field

Electric Field

An electric field exists in a region of space where a small positive charge experiences an electric force.

Line of force

1. The direction of the field is defined as the direction of the force on a small positive charge.
2. Lines of force are used to represent the direction of an electric field.
3. The lines of force are directed outwards for a positive charge and inwards for a negative charge.

Strength of Electric Field

The strength of the electric field is indicated by how close the field lines are to each other. The closer the field lines, the stronger the electric field in that region.

Field Pattern of 2 Point Sources

Ping Pong Ball in an Electric Filed

	The ball will still remain stationary. This is because the force exert on the ball by the positive plate is equal to the force exerted on it by the negative plate.
	If the ping pong ball is displaced to the right to touch the positive plate, it will then be charged with positive charge and will be pushed towards the negative plate.
	When the ping pong ball touches the negative plate, it will be charged with negative charge and will be pushed towards the positive plate. This process repeats again and again, causes the ping pong ball oscillates to and fro continuously between the two plates.

Candle in an Electric Field

	The heat of the candle flame removes electrons from the air molecules around it, and therefore ionised the molecule.
	If the candle is placed in between 2 plates connected to a Extra High Tension (E.H.T.) power supply, the positive ions will be attracted to the negative plate while the negative ions will be attracted to the positive plate.