Electric Current Chapter 7-2

Electric Circuit F A closed path through which electrons can flow F Electrons flow because of a difference in potential F When a switch is turned on it causes electron to flow

Flowing Electrons F Remember that static electricity is the build up of electrons F When the static charge causes a spark the flow of electrons that is created is very short F Not long enough to run a light or a computer

F The electrons always flow from where there are more electrons (higher potential) to fewer electrons (lower potential) F Static discharge quickly balances out the electrons and there is no more difference in potential

Current, I F The flow of electrons F The amount of current depends upon the number of electrons passing every second F Measured in Amperes, Amps, A F Measured with an ammeter

Ampere F One ampere is one coulomb of charge passing every second F One coulomb is 6.24 billion billion electrons

Potential Difference (Voltage) F The difference in potential (the energy of the electrons) between two different places F Measured in volts (V) F Sometimes called voltage F Measured with a voltmeter F Doesn’t depend upon the number of electrons only the energy the electrons carry

Batteries F Current must maintain a difference in potential or the current will stop F Batteries is a device that maintains that difference in potential

F Batteries supply the energy to keep the electrons moving, they don’t supply the electrons

F Dry cells-a positive electrode, a negative electrode, and a moist paste to pass the electrons F Wet cells-a positive plate, a negative plate, and a liquid solution to pass the electrons

Resistance, R F The opposition to the flow of electrons  Measured in Ohms,  F Copper is an excellent conductor because it has low resistance

Good & Bad Resistance F Toasters, hair dryers, Christmas lights F Wiring

Ohm’s Law F Determines a relationship between voltage, current and resistance

F If the resistance increases the current decreases F A greater voltage in a circuit causes the current to increase

George Simon Ohm F German physicist found experimentally

F The current in a metal conductor is directly proportional to the potential difference across it and inversely proportional to the resistance, Ohm’s Law F V = IR