1. Electrical Charge We can talk positive and negative electrical charges. Can we transfer charges from one object to another? –Yes Can you think of an example? –Think static electricity.

2. Static Electricity Pre scuffingPost scuffing

3. Another Law… Law of Conservation of Charge –Charge can be transferred from object to object, but it cannot be created or destroyed. Usually electrons are transferring.

4. Charges and Forces A charge can exert a force? –How? Attraction and repulsion –Opposites attract –Like repel

5. Electrical Fields These surround every electrical charge and exert the force that causes other electrical charges to be attracted or repelled. http://phet.colorado.edu/en/simulation/efiel dhttp://phet.colorado.edu/en/simulation/efiel d

6. Conductors and Insulators What is a conductor? –A material through which electrons move easily. –Examples: skin, metal objects What is an insulator? –A material through which electrons cannot move easily or are not able. –Examples: plastic, glass

7. Charging Charging by contact Charging by induction –The rearrangement of electrons on a neutral object caused by a nearby charged object.

8. Current What is a current? –The net movement of electric charges in a single direction. Current is measured in… –Amperes (A or amps) –1 A is equal to one coulomb (C) of electrical charge flowing past a point every second. A coulomb is a… –Rate

9. Voltage Difference Related to the force that causes electric charges to flow. Voltage is measured in… –Volts (V) Think of it like diffusion… High Pressure Low Pressure Low Voltage High Voltage Charge flow Current Water flow

10. Circuits Closed path that electrical current flows. Demo

11. Dry cell battery

12. Wet cell battery

13. Resistance What is resistance? –The tendency for a material to resist the flow of electrons and to convert electrical energy into other forms of energy. Ohm… –The unit used for resistance – symbol- 

14. Ohm’s Law The current in amperes in a circuit equals the voltage difference in volts divided by the resistance in ohms.

15. Calculate You measure the voltage difference of a circuit to be 5 V and the resistance to be 1000 ohms. What is the current in the current? The current through a circuit is 0.0030 A. What is the resistance of the circuit if the voltage difference across the circuit is 12 V? The current in a lamp is 0.5 A when plugged into a standard wall outlet. What is the resistance of the lamp when it is plugged into a standard wall outlet?

16. AC/DC AC –Alternating Current Changes the direction of the current –Average household outlet is 120 times/second DC –Direct Current Current never changes direction