1. ELECTRICAL CURRENT Part 1

2. Remember: Stationary electrons = Moving electrons =

3. Remember: Stationary electrons = static electricity Moving electrons = electrical current www.fotosearch.com/ comp/ART/ART158/TOT007.jpg commiechink.com/.../static.gif

4. Circuit – Definition: This is where electrons are moving in a closed and continuous pathway. There are 3 components to a circuit: 1.Source of electrons 2.Pathway through which to travel 3.Source of energy “push” or “pressure” to move electrons

5. Components of Schematic Diagrams

6. Types of Circuits Resistors in circuits can be connected in two ways Series Parallel V3V3 V1V1 V2V2 R3R3 R1R1 R2R2 I I I3I3 I2I2 I1I1

7. Series Circuit

8. Series Circuits 1.The electricity in this type of circuit only has ONE PATH to follow. 2.If the circuit is interrupted, the flow of electricity will STOP.

9. Series Circuits The resistors lie along a single pathway in the circuit. The amount of current is the same anywhere in the circuit. (same amount of current to do work; work done at the resistors) V3V3 V1V1 V2V2 R3R3 R1R1 R2R2 I In a series circuit, if lights are added, all lights would get dimmer. If lights were taken away all remaining lights would get brighter. What would happen if 1 light burnt out?

10. Parallel Circuit

11. Parallel Circuits 1.The flow of electricity has MORE THAN ONE path to follow. 2.If the flow of electricity is disrupted, the electricity may be able to find another pathway

12. Parallel Circuits – other information The current flows through many pathways. Resistors lie on different pathways. Each pathway only draws the current it needs. The current is split, but the voltage is the same through out. I I3I3 I2I2 I1I1

13. How do batteries work? A chemical reaction between lead, lead oxide, and sulfuric acid releases electrons www.tiscali.co.uk/.../ images/c00011.jpg Electrons move from negative lead electrode to positive lead oxide electrode through the sulfuric acid electrolyte

14. ELECTRICAL CURRENT Part 2

15. Types of Current DC – Direct Current, electrons flow in one direction AC – Alternating Current, electrons flow in one direction first, then in the opposite direction American homes use AC electricity that changes directions 120 times per second

16. Current – rate at which electric charge flows through the wire. Measured by counting the number of electrons passing by a specific point in the circuit in one second. Current Symbol -  Measured in amperes (amps) Amperes Symbol - A

17. Voltage – amount of electric energy available by potential difference to move electrons. More Voltage = More Work Remember (w = f  d) Voltage Symbol - V Measured in volts - V

18. Resistance – force opposing the flow of electrons in the current Good conductors = low resistance Poor conductors = high resistance Resistance Long wires > Short wires Thin wires > Thick wires Hot wires > Cool wires > Means greater than

19. Resistance symbol – R Measured in ohms Ohms Symbol -  (Greek letter omega) home.att.net/ ~basicelectronics/ohmchart.gif Born: 16 March 1789 in Erlangen, Bavaria (now Germany) Died: 6 July 1854 in Munich, Bavaria, Germany http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Ohm.html

20. Power Equation P = I × V Power (watts) = current (A) x voltage (V) “Watts” is the information that you typically associate with a light bulb

21. Ohm’s Law I = V/R V =   R R = V /  I = current V= voltage R= resistance

22. Remember Ohm’s Law V = IR For a series circuit, since the current is the same throughout the circuit, then: V = V 1 + V 2 + V 3 + etc….  V = IR 1 + IR 2 + IR 3 + etc..  V = IR eq  R eq = R 1 + R 2 + R 3 + etc… (R eq = Resistance equivalent) I V R V1V1 V2V2 V3V3 R1R1 R2R2 R3R3

23. - + V = 12v I R1R1 R2R2 R3R3 Type of circuit ___________ R eq = I = R 1 = 50  R 2 = 100  R 3 = 40 

24. - + V = 12v I R1R1 R2R2 R3R3 Type of circuit = Series R eq = R 1 + R 2 + R 3 = 50  + 100  + 40  = 190  I = V / R eq = 12v / 190  = 0.063 A R 1 = 50  R 2 = 100  R 3 = 40 