Electric Charge and Static Electricity

1. Electric Charge and Static Electricity Ch 20.1

3. Electric Charge • Property that causes subatomic particles (_____, ______) to attract/repel each other • 2 Types • Positive- Protons • Negative- Electrons • Net Electric Charge • Excess or shortage of electrons • SI Unit • Coulomb (C) • 6.24 x 1018 electrons

4. Electric Forces • Like charges • Repel • Opposite charges • Attract • Electric Force • Forces of attraction and repulsion between electrically charged objects • Charles Coulomb • Discovered electric forces are similar to the law of Gravitation

5. Electric Fields • The strength of an electric field depends on • The amount of charge that produces the field • The distance from the charge • The force depends on • The net charge in the object • The strength and direction of the fields position

6. Static Electricity and Charging • The study of the behavior of electric charges and how charge is transferred • Law of Conservation of Charge • Total charge in an isolated system is constant • 1. Charging by Friction • Ex. Rubbing a Balloon in your hair • Electrons move due to attraction

7. Static Electricity and Charging • 2. Charging by Contact • Ex. Van de Graaff generator • 3. Charging by Induction • Ex. Reaching for a doorknob after rubbing feet across carpet • Induction- transfer of charge without contact between materials

8. Static Discharge Occurs when a pathway through which charges can move forms suddenly

9. Electric Current and Ohm’s Law Ch 20.2

11. Electric Current • Continuous path through which charge can flow • SI Unit • Ampere/Amp (A) • 1 C/s • 2 Types of Current • 1. Direct Current (DC) • Charge flows in 1 direction • Flashlights, battery operated machines • 2. Alternating Current (AC) • Charge flow reverses direction • Electricity in buildings

13. Conductors and Insulators Electric Conductor Electric Insulator Material electric charge can flow easily through Cu, Ag Material electric charge cannot flow easily through Wood, plastic, rubber, air

14. Resistance • Opposition to the flow of charges in a material • SI Unit • Ohm • Superconductor • Material that has almost zero resistance when it is cooled to a low temperature • 3 Factors Affecting Resistance • Thickness • Length • Temperature

15. Voltage In order for a charge to flow in a conducting wire, the wire must be connected in a complete loop that includes a source of electric energy

16. Voltage Potential Difference Voltage Sources • Charges flow from higher to lower potential energy • PD- difference in electrical PE between 2 places in an electric field • SI Unit • J/C or Volts • Also called voltage • Battery • Device that converts chemical energy to electrical energy • Solar cells, generators

17. Ohm’s Law Voltage(V) in a circuit equals the product of the current(I) and the resistance(R) Increasing the voltage increases current Keeping the same voltage and increasing resistance decreases the current V = I x R Ex. 3 amps x 3 ohms= 9volts

18. Electric Circuits Ch 20.3

20. Circuit Diagrams • Electric Circuit • Complete path through which charge can flow • Circuit Diagrams • Use symbols to represent parts of a circuit, electrical energy and devices run by electrical energy • Open Circuit • Open switch = current stops • Closed Circuit • Closed switch = complete flow of current

21. Series Circuit • Charge has only 1 path through which it can flow • If 1 element stops working, none of the elements can operate

22. Parallel Circuit • Electric circuit with 2 or more paths through which charges can flow • If 1 element stops functioning the rest can still operate

23. Power and Energy Calculations • Electrical Power • Rate at which electrical energy is converted to another form of energy • SI Unit • J/s or Watt (W) • Kilowatt (kW) • P(watts)= I(amps) x V(volts) • Electrical Energy • SI Unit • W s • kW hr • E= P x t

24. Math Practice pg 611 1. 3. 2.

25. Electrical Safety • Electrical Energy Safety • Correct wiring • Fuses • Circuit Breakers • Insulation • Grounded Plugs

26. Electrical Safety Home Safety Personal Safety • Fuse • Prevents current overload • Blowing a fuse- melting a fuse • Circuit Breaker • Switch the opens when a current in a circuit is too high • Grounding • Transfer of excess charge through a conductor to Earth

27. Electronic Devices Ch 20.4

29. Electronic Signals • Electronics • The science of using electronic current to process/transmit information • Electronic Signal • Information sent as patterns in the controlled flow of electrons through a circuit

30. Electronic Signals Analog Signal Digital Signals Smoothly varying signal produced by continually changing the voltage or current AM radio Encodes information as a string of 1s and 0s DVDs

31. Vacuum Tubes • Change alternating current into direct current • Increase the strength of a signal • Turn a current on or off • Cathode Ray Tube • Used in computer monitors, TVs • Phosphors glow red, green or blue

32. Semiconductors • Crystalline solid that conducts current only under certain conditions • N Type Semiconductor • Current is a flow of electrons • Made by adding P to Si • P Type Semiconductor • Appears as though positive charge flows • Made by adding B to Si

33. Solid State Components Used solids instead of vacuums to control current • 1. Diodes • Solid state component that combines N Type and P Type semiconductors • Flows from N to P • Can change alternating current to direct

34. Solid State Components • 2. Transistors • Solid state component with 3 layers of semiconductors • Used as a switch or amplifier • 3. Integrated Circuits • Thin slice of Si containing many solid state components • Chips or microchips • Perform as well as a network of vacuums

35. Communications Technology • Computer • Programmable device that stores and processes information • Communication devices use microchips to make them • Portable • Reliable • affordable