1. Unit Electricity I. Electric Charge  Static Electricity  Conductors  Insulators  Electroscope

2. What do these have in common?

3. A. Static Electricity  Static Electricity  the net accumulation of electric charges on an object  Electric Field  force exerted by an e - on anything that has an electric charge  opposite charges attract  like charges repel

4. A. Static Electricity  Static Discharge  the movement of electrons to relieve a separation in charge

5. B. Conductors  Conductor  material that allows electrons to move through it easily  e - are loosely held  ex: metals like copper and silver

6. C. Insulators  Insulator  material that doesn’t allow electrons to move through it easily  e - are tightly held  ex: plastic, wood, rubber, glass

7. D. Electroscope  Electroscope  instrument that detects the presence of electrical charges  leaves separate when they gain either a + or - charge

8. II. Electric Current  Circuit  Potential Difference  Current  Resistance  Ohm’s Law

9. Potential Difference

10. B. Potential Difference  Potential Difference (voltage)  difference in electrical potential between two places  large separation of charge creates high voltage  the “push” that causes e - to move from - to +  measured in volts (V)

11. C. Current  Current  flow of electrons through a conductor  depends on # of e - passing a point in a given time  measured in amperes (A)

12. D. Resistance  Resistance  opposition to the flow of electrons  electrical energy is converted to thermal energy & light  measured in ohms (  ) Copper - low resistance Tungsten - high resistance

13. Resistance  Caused by internal friction in conductor and slows the movement of charges.  A 40 W light bulb is dim and has a higher resistance than a bright 100W light bulb.

14.  https://www.youtube.com/watch?v=KvV Th3ak5dQ https://www.youtube.com/watch?v=KvV Th3ak5dQ  Resistance video

15. D. Resistance  Resistance depends on…  the conductor  wire thickness less resistance in thicker wires  wire length less resistance in shorter wires  temp - less resistance at low temps

16. E. Ohm’s Law  Ohm’s Law V = I × R V: potential difference (V) I: current (A) R: resistance (  ) Voltage increases when current increases. Voltage decreases when resistance increases.

17. E. Ohm’s Law  A lightbulb with a resistance of 160  is plugged into a 120-V outlet. What is the current flowing through the bulb? KNOWN/UNKNOWN: R = 160  V = 120 V I = ? EQUATION : I = V ÷ R I V R WORK : I = (120 V) ÷ (160  ) I = 0.75 A

18. Superconductors Some metals have zero resistance when their temperature falls below a certain temperature (critical temperature). The range is from -458 º F to -189 º F.

19. III. Electrical Circuits  Circuit components  Series circuits  Parallel circuits  Household circuits

20.  https://www.youtube.com/watch?v=l8JS 8BbrVOg https://www.youtube.com/watch?v=l8JS 8BbrVOg  Video  https://www.youtube.com/watch?v=lYZ UXV-v71Y

21.  https://www.youtube.com/watch?v=D2 monVkCkX4 https://www.youtube.com/watch?v=D2 monVkCkX4 Circuits

22. A. Circuit  Circuit  closed path through which electrons can flow

23. A. Circuit Components A - batteryC - light bulb B - switchD - resistor

24. B. Series Circuits  Series Circuit  current travels in a single path one break stops the flow of current  current is the same throughout circuit lights are equal brightness  each device receives a fraction of the total voltage get dimmer as lights are added

25. C. Parallel Circuits  Parallel Circuits  current travels in multiple paths one break doesn’t stop flow  current varies in different branches takes path of least resistance “bigger” light would be dimmer  each device receives the total voltage no change when lights are added

26. D. Household Circuits  Combination of parallel circuits  too many devices can cause wires to overheat  Safety Features:  fuse - metal melts, breaking circuit  circuit breaker - bimetallic strip bends when hot, breaking circuit

27. IV. Measuring Electricity  Electrical Power  Electrical Energy

28. A. Electrical Power  Electrical Power  rate at which electrical energy is converted to another form of energy P = I × V P: power (W) I: current (A) V: potential difference (V)

29. A. Electrical Power  A calculator has a 0.01-A current flowing through it. It operates with a potential difference of 9 V. How much power does it use? KNOWN/UNKNOWN: I = 0.01 A V = 9 V P = ? EQUATION : P = I · V I P V EQUATION : P = (0.01 A) (9 V) P = 0.09 W

30. B. Electrical Energy  Electrical Energy  energy use of an appliance depends on power required and time used E = P × t E: energy (kWh) P: power (kW) t: time (h)

31. B. Electrical Energy  A refrigerator is a major user of electrical power. If it uses 700 W and runs 10 hours each day, how much energy (in kWh) is used in one day? UNKNOWN/KNOWN : P = 700 W = 0.7 kW t = 10 h E = ? EQUATION: E = P · t P E t WORK : E = P · t E = (0.7 kW) (10 h) E = 7 kWh