Britannica Sources used in this answer

How are electric field direction and charge sign related?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

The science behind static electricity — electricity Explanation of static electricity and its manifestations in everyday life.

The direction of an electric field is fundamentally linked to the sign of the source charge producing it. By convention, the direction of the electric field is defined as the direction of the force that would be exerted on a positive test charge placed at that point.12

The relationship between the source charge sign and the field direction is as follows:

Positive Source Charge: The electric field is oriented radially outward, pointing away from the charge.123
Negative Source Charge: The electric field is oriented radially inward, pointing toward the charge.234

When represented by field lines, these lines are depicted as originating on positive charges and terminating on negative charges. While the field itself is defined by the source charge, the force exerted on a test charge depends on its own sign: a positive charge experiences a force in the direction of the electric field, while a negative charge experiences a force in the opposite direction.125