Electricity Review

Static Electricity  Electricity that’s not moving in a path (or electricity that’s at rest) Static means not movingStatic means not moving  Also known as friction electricity  Can have positive, negative and neutral charges  Lightening Rods

Law of Electrostatics  Like charges repel and unlike charges attract

Current Electricity  A current is a flow or stream  Current electricity comes from the flow of electrons  The path that electrons move along is called a circuit  Complete circuit – electrons are moving  Incomplete circuit – electrons not moving

Batteries  Dry cells – batteries used in flashlights  Electrons leave a battery through the minus terminal  They enter through the plus terminal  Two kinds of batteries One made from dry substancesOne made from dry substances One made with liquidsOne made with liquids

Power Plants  The first large power plant was built by Edison  Power plants have giant generators Generators are large electromagnetsGenerators are large electromagnets  In most the huge generators are driven by steam engines that are fuelled by coal, oil, gas, water pressure or the energy from nuclear reactions  Hydro dams use water pressure to produce energy to spin the generator  Approximately 63% of the world’s power is generated by fossil fuel plants

Types of Energy (there are 5) 

Circuit Symbols  Lamp:Dry Cell:  Motor:Two Dry Cells:  Closed Switch:  Open Switch:  Wire:

True or False  There is no substance that gives us electricity directly.  A wire with an electric current running through it acts like a magnet.  Parallel circuits are the best way to wire a house.

Draw me a  COMPLETE series circuit with: One batteryOne battery One switchOne switch Two bulbsTwo bulbs

Draw me a:  Complete Parallel circuit with: Two batteriesTwo batteries Two switchesTwo switches One bulbOne bulb One motorOne motor

Series or Parallel??  Only one path for the electricity to follow SeriesSeries  Loads work or shut off one at a time ParallelParallel  Appliances do not share voltages ParallelParallel  Not a good way to wire a house seriesseries

Electrical Units  Amperes: The size of an electric currentThe size of an electric current  Volts: Electrical PressureElectrical Pressure  Ohm’s ResistanceResistance

 Voltmeter: Measures electrical pressureMeasures electrical pressure  Ammeter: Measures electrical currentMeasures electrical current Should never be connected to a batteryShould never be connected to a battery

Electrical Resistance  Wire Length The longer the wire the more resistanceThe longer the wire the more resistance  Wire Thickness The thicker the wire the more resistanceThe thicker the wire the more resistance

Series Circuits  Current has only one path  If one thing goes out in a series circuit then ALL things will go out  The things (such as bulbs) share the electricity that goes across the circuit The more bulbs on a series circuit the less light each bulb would give offThe more bulbs on a series circuit the less light each bulb would give off  The appliances share the electrical pressure

Parallel Circuits  The electrons have more than one path to follow Each appliance has it’s own pathEach appliance has it’s own path  The appliances DO NOT share the electrical pressure  If one bulb went out it would not affect the other bulbs  The number of bulbs would not affect the brightness of each bulb in parallel