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voltage electric pressure ; this pressure can create a flow of charge = current (slowed down by resistance) power rate at which the current moves In order to have a circuit... you must have a complete path from the positive terminal to the negative terminal What happens when you turn on a circuit? the electrons closest to the bulb flow through it first. they do not pile up Once a switch is off electrons stop moving Once a switch is on electrons start to flow circuit any path along which electrons can flow; there must be no gaps for electrons to flow and must be closed for current to flow switches a gap that can be opened or closed to control the flow of e- series circuits have a single pathway parallel circuits in branches - each is a separate path Main disadvantage of Parallel Circuits one device fails - entire circuit stops working In series, increase in devices = increase in resistance In parallel, increase in devices = decrease in resistance Flow will only continue until... there is equal potential at each end Charge flows when... there is a potential difference If we want flow to keep moving... we have to maintain a difference in charge voltage sources provide the potential difference we need to keep the current flowing (batteries) Amperes unit for current if a wire carrying the current has a net charge of zero... the wire will stay neutral epE/charge is the... electric potential or voltage charge is the electrons itself charge flow through a circuit water will flow through a pipe if there is a difference in pressure between ends, like water... charge flows through a circuit if there is a pressure (a potential difference) Electric Resistance amount of current in a circuit depends on how much pressure and how much resistance the conductor offers Resistance depends on conductivity of material, thickness of wire, length of wire and temperature (thick wire, long wires and increase of temp. = resistance) Ohm's Law current in a circuit is directly proportional to the voltage impressed across that circuit and inversely proportional to the resistance of a circuit Resistors devices in electric circuits used to limit the flow of current - (rated from few ohms to millions of ohms) What causes shock in humans? current - but a bit of both current and voltage resistance: human body (dry) = 500,000 ohms resistance: human body (wet - salt water) = 100 ohms Effects of an electric shock: overheat tissues/ disrupt normal nerve function capacitor device used to store energy and release it all at once examples of capacitors: computer on/off switches/ computer keyboards/giant lasers in labs/ camera flashes (capacitor stores a lot of energy slowly, then releases the flash) simple capacitor 2 conducting plates separated by a small distance When potential difference in plates = potential diff. in battery, the... capacitor is charged bigger battery = bigger charge closer the plates = bigger charge charge is released when a path is provided b/w the two plates increase in paths = decrease in resistance = increase in current = increase of temperature ... short circuit if bare wire is exposed you can get a very easy past and current increases If the temperature gets too high... insulation around the wire melts (overload circuit) resistive loss causes and increase in temperature Fuses and circuit breakers are devices used to prevent overloading fuse designed to only withstand a certain level of current ( increase in current can melt the fuse) circuit breakers magnets used to open the switch when current gets too high rectifier converts AC to DC internal devices run on... DC power in outlet run on... AC rectifiers open when electrons move to right ...closes when electrons move to the... left transformers used to change voltage of an AC current there is a less resistive loss if... a small current is sent at high voltage then vice versa primary coil connected to AC power source secondary coil on top of primary coil - connected to wires leading away from the device more loops to the secondary coil... increase the secondary voltage and decrease the secondary current step up transformer secondary voltage is higher than primary step down transformer secondary voltage is lower than primary