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

VoltageThe 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.

ResistanceMeasured 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 LawOhm 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!