High School Physics

Properties of the Electric field between two oppositely charged parallel plates

The electric field between two parallel plates:
– is uniform in the region between the plates
– becomes weaker at the edges (these are known as edge effects) as the field changes from the value between the plates to the value outside-the plate (often zero).

figure 1: Electric field line pattern for parallel plates.
figure 1: Electric field line pattern for parallel plates.

Electric field lines are also called “Lines of force” – why?

The field lines are also called “lines of force”. It is easy to see why. Electric forces act on charges in a field. A Field line in an electric field represents the path followed by a unit positive charge under the influence of the net electric force in the electric field, hence these field lines are called “lines of force”. The lines of force originate at a positive charge (by definition) and end at a negative charge as indicated by the arrow attached to the line.

If the line is curved, the tangent at a given point gives the direction of the electric force on a positive charge.

The density of the electric field lines (how close they are) shows the strength of the force.

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