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Electric Current Chapter 7-2 Electric Circuit A closed path through which electrons can flow Electrons flow because of a difference in potential When a switch is turned on it causes electron to flow Flowing Electrons Remember that static electricity is the build up of electrons When the static charge causes a spark the flow of electrons that is created is very short Not long enough to run a light or a computer The electrons always flow from where there are more electrons (higher potential) to fewer electrons (lower potential) Static discharge quickly balances out the electrons and there is no more difference in potential Current, I The flow of electrons The amount of current depends upon the number of electrons passing every second Measured in Amperes, Amps, A Measured with an ammeter Ampere One ampere is one coulomb of charge passing every second One coulomb is 6.24 billion billion electrons Potential Difference (Voltage) The difference in potential (the energy of the electrons) between two different places Measured in volts (V) Sometimes called voltage Measured with a voltmeter Doesn’t depend upon the number of electrons only the energy the electrons carry Batteries Current must maintain a difference in potential or the current will stop Batteries is a device that maintains that difference in potential Batteries supply the energy to keep the electrons moving, they don’t supply the electrons Dry cells-a positive electrode, a negative electrode, and a moist paste to pass the electrons Wet cells-a positive plate, a negative plate, and a liquid solution to pass the electrons Resistance, R The opposition to the flow of electrons Measured in Ohms, W Copper is an excellent conductor because it has low resistance Good & Bad Resistance Toasters, lights Wiring hair dryers, Christmas Ohm’s Law Determines a relationship between voltage, current and resistance If the resistance increases the current decreases A greater voltage in a circuit causes the current to increase George Simon Ohm German physicist found experimentally The current in a metal conductor is directly proportional to the potential difference across it and inversely proportional to the resistance, Ohm’s Law V = IR