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CURRENT ELECTRICITY Prentice Hall: Electricity and Magnetism Chapter 2, Section 2 MRS. BRUNNER SCIENCE Visit PHSchool.com for review (Use code cgd-4022) I. Flow of Electric Charges A. What is Electric Current? (think of conveyer belt) 1. continuous slow of electric charges through a material 2. static electricity does not flow (it builds up on an object) and can not power devices 3. charges flow through a wire or similar material 4. rate of electric current – amount of charge that passes through a wire in a given amount of time a. measured in ‘ampere,’ abbreviate as… b. number of amps describes the amount of … B. Current in a circuit (think of the race track) 1. electric circuit – complete, unbroken path the electricity flows through 2. charges flow from one place to another with no gaps on path 3. charges ‘flow’ – can be pushed or pulled through wire 4. circuits ‘begin and end’ at the place 5. there are circuits in every electrical device II. Conductors and insulators A. Conductors 1. material through which electricity can easily flow 2. transfers charges well from one place to another 3. conduction electrons – electrons that are loosely connected together and can flow easier, this is why a material is a conductor 4. what happens to electrons in a wire when you turn on a switch? 5. examples – B. Insulators 1. material through which electricity can not easily flow 2. electrons are… 3. examples – 4. Why don’t you get shocked when you touch an extension cord? III. Voltage A. Charges need energy to ‘flow’ in a circuit B. The force that causes the ‘flow’ is called voltage C. Potential energy – energy an object has as a result of it’s position or height, energy is stored up in the object, remember the roller coaster 1. rollercoaster at top – has high potential energy 2. roller coaster at the bottom - has low potential energy 3. the difference in these 2 potential energies is called potential difference (check out picture on pg. 49) Electric current is present in a circuit b/c there is a difference in electric potential energy between 2 places in the circuit and it is the battery that causes this Voltage causes the current in an electric circuit Voltage source – a device that creates… Voltage source examples - IV. Resistance (think of the pipe pictures) A. Current depends on resistance B. 4 Factors that determine resistance 1. other things besides voltage can affect how electricity travels through a circuit 2. resistance – measure of how difficult it is for charges to flow through a circuit 3. the greater the resistance, the less current there is 4. Ohm – the unit used to measure how much resistance there is 5. symbol for Ohm – 1. 2. 3. 4. Path of least resistance 1. if an electric charge can flow through either of 2 choices, … 2. How can the bird sit on the uninsulated wire?