1. Voltage and Electric Fields Sparks will fly

2. Going back to gravity for a moment Think about gravity a moment: Anything near the earth is pulled in by earth’s gravity There is a gravity field (force field) around the earth Anything put into this field is then affected by the gravity

3. Electric fields Likewise, a single electric charge has an ELECTRIC field around it, similar to the gravitational field around the earth We know that pairs of charges exert forces on one another So the electric field around a charge is a field that other charges would interact with if they were put into it.

4. Field lines around single charges http://downloadanswer.com/images/ab_Electricity7.JPG

5. Field lines around more charges http://www.iop.org/activity/education/Teaching_Resources/Teaching%20Advanced%20Physics/Fields/Images%20400/img_tb_4734.gif

6. About Field Lines Field lines start on positive charges Field lines end on negative charges They show the direction of the electric force that would be there if you put a small, positive charge near the original charges

7. Check for Understanding Once again with the volunteers

8. Electrical Shielding Recall that the charges placed on a conductor reside on the outside surface. Using this phenomenon, you can shield sensitive electronics from charges outside. Anything placed inside a hollow conductor will be shielded.

9. Voltage/Electric Potential The terms “voltage” and “electric potential” mean the same thing. Voltage is what provides the “pull” on charges to make them move Voltage is measured in volts

10. Voltage continued Think about what happens when you separate positive charges from negative charges. The two are attracted to one another and they want to reunite Whenever you have a separation of charges, you have a voltage. The more charges that are separated, the more they want to get back together

11. Common voltages The voltage of a AA battery is 1.5 volts The voltage of a car battery is 12 volts What is the voltage of a 9-volt battery? The voltages from the Van de Graaf Generator can be 40,000 volts or higher Lightning is millions of volts

12. Check for Understanding Once again with the volunteers