Electrostatics

•Electrostatics: the study of charges at rest.•AKA static electricity

•2 types of charge: + and –• In the majority of cases, only the negative charges are

mobile.•Neutral: equal amnts of + and – charge. No net

electric force.

Electric Force

•Non-contact force•Opposite charges attract, like charges repel.

•Attractive forces lead one to conclude that at least one object is charged.

•Repulsive forces provide convincing evidence that both objects must be charged.

•Polarization: the process of separating opposite charges in an object. (Creating poles)

Law of Conservation of Charge

•The total charge (difference between + and – charge) within an isolated system is always constant.

•Charge can’t magically appear or disappear.

Charging by friction

•Ex: shuffling across the carpet in socks.•Outer electrons are the least strongly bound and most

easily shed.•Different materials have different affinities (desire,

love) for electrons.•When in contact, one material may give up some of

its electrons to the other.•Depends on the materials.

• Insulators: hold on to outer e-

•Conductors: weak hold on outer e-. Allow charges to flow freely

Charging by Conduction

• Involves touching a charged object to a neutral object, thereby transferring some charge.

•Charge will spread out uniformly onto the second object.

•A + charged object brought into contact with something neutral will take e- away from that object, leaving both as a + charge.

•Only e- are transferred.

Charging by Induction

•A method used to charge an object without actually touching it to any charged object.

•Ground: a large object that serves as an infinite source of e- or an e- sink.

•Usually the Earth.•Grounding something allows excess charge to flow

into the Earth.