1. Day 56 Topic 8: Charges and Circuits
Electric Power, and Tying it together mathematically

2. My Goals:
1. Defining what is a circuit, the conditions needed. Proving it
2. Defining Electric Power, and how it relates to lightbulbs. Proving it
3. You do a series of tough problems to take you to the next level.

3. First Of All
Remind me… How does Voltage/Resistance/Current play a role in electricity powering a bulb?

4. First Of All
Remind me… How does Voltage/Resistance/Current play a role in electricity powering a bulb?
Current is the flow of charge, goes from high Voltage to low Voltage. Resistance works against it.

5. Remind me the difference of
Ohmic vs. Non-Ohmic
Ohmic is where temperature does not change, so the resistance stays the same with different flows through it

7. Which of these shows the pattern of current and resistance for a light bulb that heats up?

8. Which of these shows the pattern of current and resistance for a light bulb that heats up?

9. Voting
5) If you double the voltage of a circuit, how will the resistance of the circuit change?
a) Increase by double
b) Decrease by a factor 1/2
c) Increase by a factor of 4
d) Decrease by a factor of 1/4
e) Not change

10. 5) If you double the voltage of a circuit, how will the resistance of the circuit change?
E! No change. Because only 4 things affect resistance, and voltage is not one of them.

11. With your partners Questions 1, 2, 3 of HW
Notice explanations sections…this is for you to become better at explaining with your new vocabulary.

12. Answers…and questions

13. Answers…and questions
2) What potential difference is required to cause 200 miliamps to go through a resistance of 8 ohms?

14. Answers…and questions

15. Therefore
Is there any questions about what you learned last class? The ideas involved?

16. Then with your partners
Look at the next question given, and try to determine what is being asked and how to answer it
8 minutes

17. It doesn’t obey Ohms law because of the graph axis and the Ohms law equation.
Ohms law says that the R is constant (OHMIC)

18. From V=IR, look at the axis. V and I. Please solve for R from this.
From the graph, what does this represent?
SLOPE!
This is a changing slope, so non ohmic R

19. A filament in a bulb…HEATS UP. That makes it CHANGE RESISTANCE
Look at the slope…is it increasing or decreasing?
As more flow, it gets more resistance

20. You would have to get values of V and I at P, and solve using Ohms law JUST FOR THAT POINT.
Using another point to get R is wrong because R changes

21. Try

22. Look at a lightbulb…
5) If you double the voltage of a circuit, how will the resistance of the circuit change?
a) Increase by double b) Decrease by a factor 1/2
c) Increase by a factor of 4 d) Decrease by a factor of 1/4 e) Not change

23. In the bulb Current flowed from high V to low V through the metal.
The high resistance caused a lot of energy to be given off as light.
That ability is the POWER rating

24. Power
Measured in Watts
Related to Volts, Ohms and Amps
Equation(s)

29. 1st Goal: A Circuit is… any guesses/thoughts?
A closed loop for electricity to constantly flow. Must have a high/low difference.

31. GO STATE! My bottle opener has 2 plates….
What can you tell about the plates?

32. The bottle opener
Circuit diagram…
Any difference if:

33. For Example:
Copy it
Explain why ‘A’ is not a true junction here.

34. For Example:
How many amps go through B?
Find the Resistance of ‘B’

35. For Example:
Find the POWER given off by ‘B’ using TWO different equations

36. Now its time
Try the rest of these. Todays goal is UNDERSTANDING and checking.
It will involve thought, experimentation, and underlining/analyzing.
End this week on a strong note!