# PHY C17: Electric Forces & Fields (AS)

If you read my post about fields, you should remember that fields and forces are influenced by certain properties of matter. In this chapter, we look at fields affected by the ELECTRIC CHARGE.

• Electric Forces
• Electric Fields
• Electric Conductors & Insulators
• Charging objects

What is an electric force?
A force that acts on electrically-charged objects. You should know that like charges repel, while opposites attract. Head over to my A2 coverage of this chapter to see the formula describing electric force (hint: it’s almost identical to gravitational force).

DISCLAIMER:
We should really be calling this the “electrostatic force”, since it only applies when the charges are not moving relative to each other. This is because moving charges experience an additional force: the magnetic force. However, since the syllabus uses the term “electric force”, we will assume that charges are stationary or have low magnetic effects IN THIS CHAPTER ONLY. In a future chapter, we will investigate the magnetic force.

What is an electric field?
A region in space where electric forces act on electrically-charged objects.

How do we represent electric fields?
Electric field lines. There are a few rules you must obey when drawing these:

As we’ve seen in the fields post, there are 2 types of basic electric fields:

What are conductors & insulators?
These terms refer to the ability for charges to travel within a material.

With that in mind, what happens to these materials when they are placed near a charge?

If a neutrally-charged object is placed near an electric charge, the particles in that object will react accordingly:

How do you charge objects?

*Why don’t they distribute equally?
Some insulators have a higher affinity for electrons than others. See this explanation on charging by friction – AKA triboelectric charging.