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# STATIC ELECTRICITY How Would you define Static Electricity?

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STATIC ELECTRICITY How Would you define Static Electricity?

Electric Charge BASIC to all matter Different materials have different affinities for electrons.

Basic Facts About Atoms Every atom has a positively charged nucleus surrounded by negatively charged electrons. The electrons of all atoms are identical. Each has the same quantity of negative charge and mass. Protons have exactly the same magnitude charge of an electron but is opposite in its sign.

When charged particles come near one another, they give rise to two different forces. A force can pull objects together or it can push objects apart.

Law of Electric Charge 1:Like charges repel one another 2: Unlike charges attract one another

Why do balloons stick to the wall after being rubbed on hair or fur?

How Can This Happen?

Static Electricity The buildup of electric charges on an object The electric charges build up because electrons have moved from one object to another.

Three Ways of Creating a Charge Rubbing two objects together-FRICTION-- TRIBOELECTRIC Conduction– transferring a charge by TOUCHING Induction-- Inducing a charge-NOT TOUCHING

Friction Transfer of electrons by rubbing.

Rubbing Separates charges on Objects One object loses electrons while the other object gains these electrons. The object that loses electrons has an overall positive charge. ONLY THE ELECTRONS MOVE!!!

A van der Graff Generator rubs electrons off a rubber band. These electrons are transferred to the dome.

Van de Graff Generator

CHARGING BY CONDUCTION Charging a neutral body by touching with a charged body

Conduction Conduction transfers the electrons to another object through actual contact.

What Is Happening?

Conservation of Charge It is important to note that when we charge something, no electrons are created or destroyed.

Charging by INDUCTION Charging an object by NOT Transferring Charges.

What are the charges doing?

Electric Fields Charged Particles have fields around them As the distance from a charged particle increases, the strength of the electric field decreases.

Coulomb’s Law q1q2 F = k ——— d2

Electric Discharge The rapid discharge of electrons. Examples: –Spark that jumps between your finger and a doorknob –lightning

VOLTAGE Also known as POTENTIAL DIFFERENCE Voltage “acts” like a force in electrical circuits.

VOLTAGE Electrical Potential difference or energy per charge is called a volt

Separation of Charges Look at the picture: establish a relationship between Energy, Voltage and Distance for two charge plates..

Electricity may be defined as the energy associated with electrons

DANGER!!! STATIC CHARGES 200 years ago, young boys called powder monkeys ran below the decks of warships to bring sacks of gunpowder to the cannons above. It was the ship law that this task be done barefoot.

DANGER!! STATIC ELECTRICITY Always touch something metallic before grabbing the pump handle if you think you have built up a static charge….

DANGER!!! STATIC Never pump gas without discharging the static charge first

1 Coulomb 6.25 X 10 18 electrons

Coulomb’s Law The amount of force the a tiny sphere with a charge q1 exerts on a second sphere of q2 is inversely proportional to the square of the distance. If I double the distance the force decreases to one fourth of the original force The Force between the spheres is directly proportional to the charge.

Coulomb’s Law q 1 q 2 F = k ——— d 2 F=force k=9 X 10 9 N*m 2 /C 2 q 1 = 1 st charge in Coulombs q 2 = second charge d= distance in meters

Electric Field All charges create an area in all directions around it that an electric charge can be detected.

Electric Fields Electric Field strength measured in N/C E= F/q

Electric Field Lines Radiate from the positive charge to the negative charge. Defined by the path of a positive test charge.

Electric Field Lines Determined from + test charge

Electric Field lines Show forces around a point charge that go from positive to negative.

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