1. Series and Parallel Circuits

2. Electric Power How was power define before?
Time rate of doing work or using energy
Electric Power - Rate at converting electrical energy into other forms of energy.
P = W/t or P = E/t
Unit: watt, w = J/s
60w light bulb converts 20 J of electric energy to light and heat each second.

3. P = E t
V = E Q
E = Q V
P = Q V t
P = I V

4. Example
What is the resistance of a 1200w electric frying pan that draws a current of 11a?
9.9 Ω

5. Problem Set 1
1. An appliance draws 13 a when connected to a 110v circuit.
a. What is the power of the appliance?
b. What is its resistance?
2. What is the power of a light bulb that has
a resistance of 190 in a 120 v circuit?

6. What does the power plant sell you?

7. Problem Set 2
If the local power company charges $0.080/kw * h, how much (to the nearest cent) will it cost to use:
a 75 W CD player for 5.0 hours?
a 2.3 kw oven for 45 minutes?
a TV drawing 2.0 amps of current in a 120 v circuit for 3.5 hours?

8. Series Circuits
Resistors are connected in a single path.

9. Parallel Circuits Resistors are connected in separate branches.
There is more than one path for current.

10. Series Circuit Lab
Make the following circuit. Remember an ammeter goes into the circuit as shown in the diagram. A

11. Observe the brightness of the bulbs.
Now add a second resistor in the circuit, as shown in the diagram below.
Observe the brightness of the bulbs. A

12. Observe the brightness of the bulbs.
Now, add a third resistor into the circuit, as shown in the diagram below.
Observe the brightness of the bulbs.
Remove one of the bulbs and record the results. A

13. Part B
Construct the following diagram with the ammeter at the AT location.
Next, move the ammeter to the A1 and A2 sites and record the current.

14. Part C
Place the Multimeter in the voltage terminal and switch the dial to Voltage setting.
Build the following circuit and place the voltmeter on either side of the battery at the VT. Remember a voltmeter is connected around the battery or resistor since it measure a difference in potential energy between two locations.
Now move the voltmeter to V1 and V2 locations.

15. Parallel Circuits Lab
Place the multimeter back in the ammeter setting by switching to terminals and the dial setting to A.
Construct the circuit depicted in the diagram below.
Observe the brightness and the current and record your observations. A

16. Add a second resistor in parallel as depicted in the diagram below.
Observe the brightness of the light bulbs and the current and record your observations. A

17. Add a third bulb in parallel. Make observations and record.
Unscrew a bulb and make observations. Record
Answer conclusion questions. A

18. Part B
Remove one of bulbs in the circuit and keep the ammeter in the same position AT.
Now, move the ammeter to the other two sites to measure the current in different paths.

19. Part C
Switch the multimeter to the voltmeter setting by moving the terminals and turning the dial to the voltage setting.
Place the voltmeter in parallel with the battery by reading the VT, terminal voltage.
Move the voltmeter to the other two locations, V1 and V2.

20. Conclusions
Use ohm's law to calculate the resistance in the different positions.
Answer the Conclusions.

21. Series Circuits Current is the same in all parts of the circuit
It = I1 = I2 = ...

22. Series Circuit
Voltage drops across resistors adds up to the total voltage provided by the battery.
Energy is conserved.
Vt = V1 + V2 + V3

23. Series Circuits
Total resistance is found by adding the resistance of each device.
Rt = R1 + R2 + R3

24. RT _____ VT _____ IT _____ V1 _____ V2 _____ V3 ____

25. Video Problem Set 3

26. Problem Set 4

27. What would happen if your house was wired in series circuits?
What would happen as you added more and more things to the circuit?
What would happen if one appliance malfunctioned?

28. Current in Parallel Circuits

29. Current in Parallel Circuits
Current in each branch adds up to the total current of the circuit.
Electric charge is conserved

30. Current in Parallel Circuits
Current in each branch adds up to the total current of the circuit.
Electric charge is conserved.
IT = I1 + I2 + I3 + …

31. Voltage in Parallel Circuits

32. Voltage in Parallel Circuits
Voltage drops across resistors in each branch equals total voltage provided by the battery.
VT = V1 = V2 = V3 = …

33. Resistance in Parallel Circuits
Equivalent resistance is less than resistance of each resistor alone.
Req R R R3 = + + + …

34. Examples What is the equivalent resistance of:
Two 10Ω resistors in parallel? 5Ω
Two 8Ω resistors in parallel? 4Ω
Three 9Ω resistors in parallel? 3Ω
A 60Ω, a 30Ω , and a 20Ω resistor connected in parallel?
10Ω

35. Problem Set 1

37. Equivalent Resistance
The two resistors in parallel can be replaced with a single resistor

38. Example

39. Problem Set 2

40. Problem Set 3

41. In a series circuit, the voltage drops across the resistors,
In which type of circuit is there only one path for the charges to travel?
In a series circuit, the voltage drops across the resistors,
Equals the voltage of the battery
Adds up to the voltage of the battery
Is less than the voltage provided by the battery
When resistors are connected in ______, voltage stays the same in all branches.
The term equivalent resistance is used for resistors connected in _____.
Our homes are wired in ______.