Electricity (resistance, current, voltage) Instructor: Shelia Chase
Electricity A form of energy resulting from the existence of charged particles (such as electrons or protons), either statically or as an accumulation.
Electric Current • The flow of electric current • Charge flows when there is a potential difference, difference in potential (voltage) between ends of a conductor • In solids, electrons carry the flow • In fluids, positive and negative ions as well as electrons may flow
Example If one end of a wire were connected to the ground and the other end placed on a Van de Graaff generator that is charged to a high potential, charge would flow through the wire. This would be brief flow, to have longer flow you would need to maintain the potential difference.
Potential Difference http://www.youtube.com/watch?v=F1p3fgbDnkY
Voltage The voltage source is something that provides the potential difference. If you charge a metal sphere positively, and another negatively, you can develop a large voltage between them. http://www.youtube.com/watch?v=1xPjES-sHwg
Resistance The current also depends on the resistance that the conductor offers to the flow of the charge- the electrical resistance.
Resistance • Similar to the rate of water flow in a pipe • Thick wires have less resistance than thin wires • Longer wires have more resistance than short wires.
Resistance Measured in units called ohms, after Georg Simon Ohm, a German physicist who tested different wires in circuits to see what effect the resistance of the wire had on the current.
Ohm’s Law Ohm discovered that the current in a circuit is directly proportional to the voltage impressed across the circuit and is inversely proportional to the resistance of the circuit, current = voltage/resistance
Physics is fun!