ELECTRICITY

Electric Charge Protons and electrons both have the property of charge.

Recall that protons are positive and electrons are negative.

A force of attraction exists between things that have opposite charges.

A force of repulsion exists between things that have same charges.

Electric Field An electric field

extends outward through space from every charged particle. As things move toward each other the charge may move from one object to another.

The electric field is strongest near the charged particle.

Static ElectricityBecause electrons can move freely things can

become either positively or negatively charged.

Charge is only being transferred from one object to another. This is called the Law of Conservation of Charge.

Static electricity – is the buildup of electric charges on an object.

Methods of Charging Friction – when two objects are rubbed together. Example:

balloon on your hair. Conduction – the direct contact of objects. Example:

plugging something in. Conductors – allow electricity to go through easily Insulators – do not allow it to move through.

Induction – the jumping of electricity from one object to another. Example: a negatively charged rubber rod can pick up tiny pieces of paper.

Electric DischargeElectric discharge – theloss of static electricity aselectric charges move offan object. Sometimesslow and quiet, or rapidwith a spark of light,

shock,or crackle of noise.Example: lightning or asimple static shock

Circuits A circuit – is formed when

a wire is connected to the terminals of a source forming a complete path.

Electric current – the amount of charge that passes a given point per unit of time.

The symbol for current is I

Things to know… Georg Simon Ohm established the relationship between electric current and potential difference. Ex. 8 v battery vs 4 v battery. Resistance – R opposition

to the flow of electric charge (example: copper low: iron high) The unit to measure resistance is the ohm

Ohm’s law – the current in a wire is equal to the voltage divided by resistanceI = V/R

Current direction DC (direct current) –

electrons always flow in the same direction. Example: batteries

AC (alternating current) electrons move back and forth, reversing direction regularly. (example: current in home changes direction every second 120x)

CircuitsElectric circuit –

consists of a source of energy; a load; wires, and a switch.

Sources: battery, thermocouple, photocell, or electric generator

Load – uses the electricity

switch

source

loadwire

Series vs Parallel Series circuit – only one path to take; if any part

goes out the whole thing goes out. Example: old Christmas lights

Parallel circuit – separate paths. Example: circuits in homes.

Fuses – protect against too much current flow, they burn out and can be a hassle

Circuit breakers – like fuses but do not burn out. Take out packet & complete page 2 Electrical

Currents

Series vs Paralleldraw these

Power Electric Power – a measure of the rate at

which electricity does work or provides energy. Measured in watts.

Power = voltage x current Energy = power x time

Electric Safety Never handle when wet or near water Never run wires under carpet Never overload circuits Repair worn out wires Put nothing in electric sockets that does not belong Never go by fallen wires or power lines In lightning storms get down to the ground by crouching down and

stay away from trees. Safest spot in a lightning storm is inside a car.