Probe the fundamental principles and applications of electricity

Electric Charge Charge Force Fields Atoms lose electrons and now have a positive charge Shortage of electrons causes an electric charge Force Like charges repel Opposite charges attract Fields Area around an electric charge that effects others Depends on amount of charge and distance

Static Electricity and Charging Charges between stationary objects Charging by friction Sliding an object across something to pick up a charge Rubbing a balloon on hair, socks on carpet Charging by contact Pick up a charge by touching something that has a charge Charging by Induction No contact needed to change charge of objects

Static Discharge Law of conservation of charge-total charge is constant Discharge occurs when charges can change suddenly Examples Lightning-cloud is negative, ground is positive Shock from doorknob-finger is negative, doorknob is positive

Current Electric current Alternating Current Direct Current Continuous flow of electric charge Unit is ampere, A Current flows in opposite direction of charge flow Alternating Current Charge regularly reverses direction What comes out of a socket Direct Current Charge flows in one direction Batteries

Conductors & Insulators Electrical conductor Charge flows easily Metal, copper, silver Sea of electrons in metals Electrical insulator Does not flow easily Wood, plastic, rubber, air

Resistance Resistance Superconductor Inability of electrons to flow easily Thickness, length, and temperature affect resistance Thick wire-less resistance Long wire-high resistance High temperature-high resistance Measured in Ohms, W Superconductor Super cooled object that has no resistance Cooled to below 138K

Voltage & Ohm’s Law Potential difference Sources Ohm’s Law Difference in electrical potential energy between two places Measured in volts, V Call it voltage Sources Batteries, convert chemical to electrical energy Solar cells convert solar to electrical energy Generators convert mechanical to electrical energy Ohm’s Law Increasing voltage increases current Increasing resistance decreases current Voltage is the product of current and resistance V=I x R

Circuits Circuit diagram Series Parallel Shows the flow of current, resistors, sources, and devices in a circuit Open circuit-charge cannot flow completely “Off” Closed circuit-charge can flow completely “On” Series Charge has only one path to move If one element stops, all stops Current the same through each element Voltage different through each element Christmas lights Parallel Two or more paths If one element stops, others can still work Current different through each element Voltage the same through each element Houses on parallel circuits

Power and Energy Power Energy Rate at which electrical energy is converted Measured in Watts P=I x V Energy Amount of power used over time Measured in kilowatt Hours, kWh E=P x t

Safety Fuse Circuit breaker Personal safety Prevents overloading of a circuit Metal melts causing an open circuit “blowing a fuse” Circuit breaker Switch that opens when current is too high Must be reset Personal safety Insulation on wires Grounding-excess charge transfers to the earth Ground-fault circuit interrupter-opens the circuit if the currents are not equal