Unit 3Characteristics of Electricity

Unit 3• Electrical energy has allowed us to develop technologies that

have enhanced our way of life

Hybrid• Hybrid vehicles are often used today where, one part of the

vehicle uses a gasoline powered motor and also energy from an electrical motor

• As oil prices continue to rise and the environmental concerns are addressed, using electricity for transportation will become even more important

Chapter 7Static Electricity is produced by electron transfer

Objectives

By the end of the lesson you should be able to:• State the 3 Laws of Electrostatics• Describe a Coulomb• Describe how a static charge is created, measured and

transferred• Describe insulators and conductors

Physics Intro• Physics: the study of energy and its uses

• For this unit we will be focusing on Electrical Energy

Electricity• Electricity is the study of the electron and its uses

• Where is electricity used?• Why do we get shocked?• How do light bulbs work?• How does electricity actually flow?

Remember• An atom has 3 subatomic particles

Proton Neutron Electron

• There are positive and negative charges• Electrons move fairly easily – Proton and neutrons do not!

• Add electrons = negative• Remove electrons = positive

Electrostatics• Electrostatics = the study of non-moving electrons

• The Laws of Electrostatics:• Opposite charges attract• Like charges repel• Neutral objects are attracted to any charge

• An induced charge results from the movement of electrons by charged objects nearby, not by direct contact!

• An electroscope measures the amount of static electricity

Static Charge• An excess of positive or negative charges that stay in place on

an object for a relatively long period of time.

Examples: Lightning, static cling in clothes, receiving a shock when touching a door handle

The Coulomb• Charles Coulomb: lived during the 1700s

• Developed a way to measure the quantity of electrons• Named the unit the Coulomb (C)• One C equals 6.25x1018 charges

Since 1 electron = 1 negative charge1 C = 6.25 x 1018 electrons!!

Did you know• Lightning contacts the ground at a speed of approximately

220000 km/h

Positive and Negative Charges

• Charles Du Fay (1698 – 1739) discovered two types of static electric charges. Benjamin Franklin (1706 – 1790) named the two charges positive (+) and negative (-) charges.

Chemistry Recap• Atoms are made up of protons ( +), neutrons

(0), and electrons (-). • # protons = # electrons, the atom is neutral.• Electrons orbit the nucleus and move quite

easily.• Movement or transfer of electrons from one

atom to another changes the charge on the atom.

A Neutral Atom (Lithium)

Chemistry Recap• When an atom loses electrons, the atom becomes more

positive.• When the atom gains electrons, it becomes more negative.• Neutral objects do not have a charge.

Conductors

• Allow electrons to transfer freely• Metals are excellent conductors because they can give electrons

easily eg. Copper or aluminum

Insulators• Materials that do not allow electrons to move easily from one

location on an object to another (electrons tend to stay with the atom they are attached to).

Examples: glass, plastics, ceramics, dry wood.

Creating Static Electricity• Friction between two objects causes one object to lose

electrons and the other object to gain electrons

Generating Static Charge• Friction causes objects to

become charged• For example, the static

charge in clouds is produced due to the friction as hot air rises rapidly in the cloud banks

• The Van de Graaff generator uses friction to produce a large static charge on a metal dome using a moving belt

Applications• Devices in chimneys use static charge to remove small

particles of dust• Plastic sandwich wrap clings use static electricity• Air Ionizers clean the air by attracting charged particles in the

air• Static electricity is used in painting automobiles• Refuelling

Dangers of Static Electricity• Before pumping fuel you need to get rid of static electricity

because they can cause an explosion• Allowing charge to flow into Earth’s surface is called grounding• Lightning rods on houses and large buildings provide a ground

rather than hitting the building