ELECTRICITY

1. Electric Charge  Atoms are made up of 3 particles –Neutrons have a neutral charge. –Protons have a positive charge. –Electrons have a negative charge.  An atom is electrically neutral if the number of electrons EQUALS the number of protons  However, atoms sometimes LOSE or GAIN electrons.  When excess (or extra) electrons are stored, an overall NEGATIVE (-) charge is achieved

Charges  Handy rule : Opposites attract And likes repel

2. Electric fields  Every electric charge is surrounded by an electric field which can exert a force on objects which come into it. These fields can push or pull over distances

2 types of electricity  Static electricity  Electric current

 Static electricity is an accumulation of electric charges on an object. -  transferred Negative ChargeNeutral Charge

Charging objects  Objects can become charged by a variety of methods  2 ways are –Charging by CONTACT –Charging by INDUCTION

Charging by Contact  Objects touch or rub against each other (contact) and charge is transferred

Charging by Induction  Occurs when a charged object is brought near a neutral object. The charges in the neutral object rearrange themselves and present the illusion of a charge.

 Once objects are charged, they can then transfer their charge…sometimes, suddenly, in what is called a STATIC DISCHARGE.

Electric Current  Is the flow of electrons through a conductor, such as a copper wire

Conductors and Insulators Conductors = materials which allow excess electrons to easily move through them. Examples : metals, water The Earth also functions as a conductor.

Conductors and Insulators Insulator = a material that doesn’t allow electrons to move through it easily Examples : plastic around wires, wood doors, fiberglass, rubbers Notice what the handles are made of. Why?

Electroscope  A device made up of two thin metal leaves attached to a knobbed metal rod. The leaves can move and hang straight down when not charged. This device is used to detect electric charges.

Lightning Large static discharge Air masses move and swirl Top + Bottom - Negative charge induces a + charge on ground (repel e-)

Bottom accumulates enough - Electrons in cloud attracted to ground When electrons get close to ground Positive charges are attracted Connection made = lightning

Electric charges move through air  collide with atoms/molecules Collisions cause atoms/molecules to emit light

Powerful sound waves Electrons are ripped off atoms in the air Produce great amounts of heat

Warms surrounding air to 25,000 C (2.5x hotter than Sun surface)

Heat causes air in path to expand rapidly  sound waves = Thunder

Earth is a large neutral object Connection (conductor) will transfer any excess electric charge “Grounding” – the act of making a connection for an electric charge to go to the Earth (Lightning rods)