Electric Fields

Chapter 21

21.1 Creating & Measuring Electric Fields

The electric force varies inversely as the square of the distance between two point objects.

How can a force be exerted through empty space?

Michael Faraday suggested because of an electrically charged object changing the properties of space

Electric Field

The changed property of space is the electric field

The electric field means that the interaction is not between two objects, but between an object and the field at the location of the object.

Electric Field

How is the electric field measured? Place a small positively charged object in the

space, if there is a force on the object, there is an electric field.

According to Coulomb’s law the force and the charge are directly proportional.

So divide F by q (test charge) and get a vector quantity representing the electric field at a certain point.

Electric Field Strength

The direction of an electric field is the direction of the force on a positive test charge.

The magnitude of the electric field is measured in N/C.

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q

FE onq

Picturing the Electric Field

Electric field is a vector quantity so use an arrow to represent the direction of a positive test charge and the number of arrows and spacing between lines represent the strength

These are electric field lines