Cavallaro CPP Electrostatics

aka ‘electricity at rest’ or static electricity 2 categories for electricity: static & current –Current refers to the flow of electricity through a conductor~What is the main characterisitic of conductors? Elaborate & remember repeating theme: micro  macro –Static electricity is electric charges that accumulate in a given area

Cavallaro CPP Review of Basic Chemisty: Most matter is electrically neutral which means there exist an equilibrium amongst the charged particles that compose neutral matter; total charge is zero due to this electrical neutrality Electric charge is a fundamental property of matter Electric charge comes in two forms: positive and negative ~protons are positively charged & located with in atomic nucleus ~electrons are negatively charge & located outside the nucleus within the electron cloud ~in a neutral atom protons=electrons ~once an atom loses or gains electrons it becomes a charged particle called an ion Why would an atom lose or gain e-s? What are the 2 types of ions?

Law of Electric Charges Even if ions (charged particles) are not touching they can still exert a force on each other due to what type of force? The Law of Electric Charges states: like charges repel, opposite charges attract A positive and a negative charge will move closer together Two negative charges will repel (move away) Two positive charges will repel (move away)

The Electric Force & The Electric Field The force between charged objects is called the electric force. The strength of the electric force depends on two factors: 1)The size of the charge  the larger the charge, the greater the electric force 2)The distance of the charges  the closer the charges, the greater the electric force –This concept is illustrated with Coulomb’s Law

Coulomb's law states that: The magnitude of the electrostatic force of interaction between two point charges is directly proportional to the scalar multiplication of the magnitudes of charges and inversely proportional to the square of the distance between them. The force is along a straight line joining them. If the two charges have the same sign, the electrostatic force between them is repulsive; if they have different sign, the force between them is attractive.

Coulomb's law can also be stated as a simple mathematical expression. The scalar & vector forms of the mathematical equation are

Static electricity Static electricity is a build up of electric charges on an object. Charges that build up as static electricity eventually leave the object. The loss of static electricity as charges move off an object is called electric discharge.

Electricity in nature is called lightening

Lightning – An example of Electric Discharge During a thunderstorm, water droplets and air move within the storm cloud. As a result, negative charges build at the bottom of the cloud and positive charges build up at the top. The negative charges at the bottom of the cloud induce a positive charge on the ground. This large difference in charge causes lightning.

Three Ways to Transfer Charge 1)Friction  rubbing two objects together can cause electrons to be transferred from one object to another. Ex: Rub a balloon on your head. The electrons will be transferred from your hair to the balloon.

2) Conduction  occurs when electrons are transferred from one object to another by direct contact. Example: Touching a negatively charged plastic ruler to an uncharged metal rod causes the electrons in the ruler to travel to the rod. The rod becomes negatively charged by conduction.

3) Induction  occurs when charges in an uncharged object are rearranged without direct contact with a charged object. electrons Ex: a negatively charged balloon induces a positive charge on a small section of a wall because the electrons in the wall are repelled from the negatively charged balloon and move away from the balloon.