1. Electricity (resistance, current, voltage) Instructor: Shelia Chase

2. Electricity A form of energy resulting from the existence of charged particles (such as electrons or protons), either statically or as an accumulation.

3. 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

4. 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.

5. Potential Difference http://www.youtube.com/watch ?v=F1p3fgbDnkY

6. 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=1x PjES-sHwg

7. Resistance The current also depends on the resistance that the conductor offers to the flow of the charge- the electrical resistance.

8. 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.

9. 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.

10. 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

11. Physics is fun!