Electric Field and Field Lines

Mapping the push a charge would feel.

The electric field at a point is the force a small positive test charge would feel there, divided by its size. Field lines start on positive charges and end on negative ones. They never cross, and where they are close the field is strong.

Between two parallel plates the field is uniform. Inside a charged conductor at rest the field is zero and all the charge sits on the outside, which is why a metal enclosure shields its contents from external electric fields.

• Field direction is the direction of force on a positive charge.
• Units: newtons per coulomb or volts per metre.
• A metal cage shields its inside from electric fields.

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