17.2 - Electric Fields

Electric fields and field lines

• An electric field is created around any electrically charged object.
• It's the region around the object where another charge feels a force.
• The closer to the object, the stronger the field.

Field lines

Electric fields are represented using field lines. Field lines:

• Point from positive to negative (the direction of the force on a positive charge)
• Meet the surface of the charged object at a right angle
• Have arrows showing the field direction
• Show field strength by their spacing - the closer the lines, the stronger the field

Field patterns to recognise

• An isolated point charge
• A charged conducting sphere (which has the same field pattern as a point charge)

The uniform field between parallel plates

• The electric field between two oppositely charged parallel plates is uniform: its strength and direction are the same everywhere between the plates.
• A uniform field is drawn as parallel, evenly spaced field lines running from the positive plate to the negative plate.
• A charged particle placed in a uniform field feels a constant force everywhere between the plates.