CHAPTER 6

1. CHAPTER 6 ELECTRICITY

2. Do you remember that … • Electrons and protons have electric charges. • Electrons = have negative electric charges • Protons = have positive electric charges • Electric charges produce an “electric force”. • “Like charges repel; opposite charges attract.”

3. Static Electricity or Electrostatic Charge • - is confined to an object and does not move • - is an accumulated charge at rest • Coulomb – is the quantity of electrons that have been transferred onto or away from an object

4. Electric Current – is the flow of charge • Ampere (amp) – is the unit for current • - is the same as coulomb/sec • Insulators – have high electric resistance • Conductors – have low electric resistance

5. Direct Current (DC)= currents that always move in one direction • Alternating Current (AC) = current that moves electrons alternately one way and then another • Volt = is the unit of voltage

6. An electric circuit must have a battery or an electric generator that acts as a source of energy as it forces charges (electrons) out of one terminal through the wires. • Voltage = is the energy transfer per coulomb • 1 Volt = 1 Joule/1 coulomb

7. Electricity flows when a circuit is complete • Switches = serves to open or close circuits only and nothing else • Ex. The light switch in your home turns your lights on or off. So you are either opening the circuit or closing it when you flip the switch.

8. Resistor – is a two-terminal electronic component that produces a voltage across its terminal that is proportional to the electric current that is passing through it.

9. RESISTORS

10. The first band gives the first digit. • The second band gives the second digit. • The third band indicates the number of zeros. • The fourth band is used to shows the tolerance (precision) of the resistor

11. Color Codes of Resistors

12. Function of Resistors • Resistors restrict the flow of electric current. • For example: a resistor is placed in series with a light-emitting diode (LED) to limit the current passing through the LED.

13. Connecting and Soldering • Resistors may be connected either way round. • They are not damaged by heat when soldering.

14. Common Circuit Parts • 1. Voltage Source – “Battery” • 2. Conductor – “Wiring” • 3. Load – “ light bulb” • 4. Switch – ( the switch you see on the wall)

15. Series Circuits • A series circuit allows electrons to follow only one path. All of the electricity follows 1 path. The loads in a series circuit must share the available voltage. In other words, each load in a series circuit will use up some portion of the voltage, leaving less for the next load in the circuit. This means that the light, heat, or sound given off by the device will be reduced.

16. SERIES CIRCUITS • In a series circuits, if any bulb is disconnected or burned out, all the bulbs go out. • This is because all the electricity flows through each connected part. • For the same reason, adding more bulbs to the circuit causes all the bulbs to dim. • Each resistor cuts down the available flow of electricity.

17. Series Circuits • NOTE!!! • Only one wire connects two bulbs to each other.

18. SERIES CIRCUITS

19. Series Circuit

20. Parallel Circuits • In parallel circuits, the electric current can follow more than one path to return to the source, so it splits up among all the available paths. Some current follows path #1 (top loop), while the remainder splits off from #1 and follows path #2 (bottom loop). Across all the paths in a parallel circuit the voltage is the same, so each device will produce its full output.

22. NOTE!!! • In a parallel circuit components are connected with common polarities (positive to positive and negative to negative).

23. Parallel Circuits • In a parallel circuit, the wires are arranged to bypass a burned out or missing bulb. • Therefore, adding more bulbs (that have the same resistance) to the circuit does not noticeably affect the brightness. • Each bulb beyond receives the same amount of electricity.

24. Parallel Circuits • NOTE!!! • In a parallel circuit, the electricity flows to and around each bulb. • Each bulb is connected to each other with two wires!!!

25. Chapters 9 and 10 Water, Solutions and Chemical Reactions

26. Water • Best Solvent - Why? • Because it is cheap and plentiful. • Compounds that dissolve in water are considered POLAR compounds. • Compounds that do not dissolve in water are considered NON-POLAR compounds.

27. Solubility Rule • “Like Dissolves Like.” • Polar solvents dissolve polar solutes. • Ex. Sugar dissolves in water • Non-polar solvents dissolve non-polar solutes. • Ex. Grease dissolves in gasoline.

28. Solutions • Strong Electrolytes – conduct electricity • Has lots of ions in soln. bec. solute totally ionized • Weak Electrolytes – weakly conduct electricity • solute only partially ionized so few ions in soln • Non-electrolytes – do not conduct electricity • has no ions in solute because solute didn’t ionize

29. Note • Compounds containing metals totally ionize in solution and are strong electrolytes. • Acids also ionize in solution but some do not totally ionize and are therefore weak electrolytes. The strong acids are strong electrolytes because they totally ionize in solution.

30. Common Reactions • 1. Combustion – must have O2in the reaction and must produce CO2, H2O and heat (although heat if often not shown in the equation) • 2. Neutralization – must involve and acid and a base • 3. Precipitation – must produce an insoluble compound

31. pH • Indicates the acidity or basicity of a compound • Normal range is from 0 – 14 at 25 oC

32. Colligative Properties • Properties that depend upon the number of ions in solution rather than the identity of the solute. • The addition of a non-volatile solute to a solvent will: • Decrease Freezing Pt. • Increase Boiling Pt.