CHARACTERISTICS OF ELECTRICITY

Chapter 7: Static Charge is produced by electron transfer.

Electrostatics Kit

Why must there be contact between the two objects to produce a charge?

How can the charged object lift the tiny pieces of paper off the table?

Static Charge

Also known as static electricity is electric charge that is collected and held in one place. (not moving)

Atom – Positive & Negative All matter is made up of tiny particles

called atoms. Atoms are made up fo a nucleus which

contains neutrons (neutral charge) and protons (positive charge).

Around the nucleus are much lighter particles called electrons (negative charge).

Model of an Atom

Charge

How can an object become charged?

Adding or removing electronsWhen electrons are added to an object it

becomes negatively charged.When electrons are removed from an object

it becomes positively charged.

Simulation

http://phet.colorado.edu/en/simulation/balloons

Activity 7-1B

Complete Activity 7 -1 B, p. 231

Insulators & Conductors

InsulatorMaterials that do not allow charges to move

easily within the material.○ Ex: Plastic, Rubber

Can an insulator become charged? What happens to the charge on an

insulator?

Conductors

Materials that allow electrons to travel freely.Ex: Metals, Water

What happens when a conductor becomes charged?

Can you identify the conductors & insulators in a wire?

Checkpoint! One of these isolated charged spheres is

copper and the other is rubber. The diagram below shows how the charge is distributed. Label which is copper and which is rubber and support your answer with an explanation.

Measuring Charge

A neutral object has the same number of electrons and positive.

A charged object has more electrons than protons if it is negatively charged and more protons than electrons if it is positively charged.

How do we measure the charge?

Coulomb

Unit of charge is called the coulomb (C) named after Charles Coulomb.

1 C of charge = 6250000000000000000

electrons removed or added. A lightning bolt has a charge between 5

to 25 C.

Van de Graff Generator

http://www.youtube.com/watch?v=sy05B32XTYY&safety_mode=true&persist_safety_mode=1&safe=active

Grounding

Objects with an excess of charge - either positive or negative - can have this charge removed by a process known as grounding.

Grounding is the process of removing the excess charge on an object by means of the transfer of electrons between it and another object of substantial size. (usually the earth)

Why?

When an oil tanker car has arrived at its destination, it prepares to empty its fuel into a reservoir or tank. Part of the preparation involves connecting the body of the tanker car with a metal wire to the ground. Suggest a reason for why is this done.

Check your Understanding P. 237 #2, 3, 5, 6, 7, 10, 14, 15, 16

Electric Force

Force is defined as a push or pull. An electric force is an action-at–a-

distance force which can apply force to an object without touching it.

Laws of Static Charge

1. Opposite Charges Attracthttp://www.mrwaynesclass.com/teacher/elec

trostatics/demos/home.html

2. Like Charges Repel

3. Neutral Objects are attracted to charged objects.

http://www.mrwaynesclass.com/teacher/electrostatics/ceiling/home.html

Laws of Static Charge

Charles Coulomb discovered the laws and also discovered that:If you increase the amount of

charge you increase the amount of force.If you increase the distance

between charged objects, you

decrease the electric force.

Charging by Conduction

Charging by conduction involves the contact of a charged object to a neutral object.

Charging by Conduction

When charging something by contact it is important to note the following properties:

1. The objects must actually touch and transfer some electrons.

2. The objects become charged alike.

3. The original charged object becomes less charged because it actually lost some charge.  Therefore, there is a limit to how many times it could be used to charge something without being recharged.

Charging by Induction

A neutral object is charged by bringing a charged object close to but do not touch the object.

The neutral object becomes charged where the charged object was brought near.

The object has a whole remains neutral.

Photocopier

Read p. 241.