1. Do Now: Calculate the resistance of the conductor whose graph is given above.

2. Bell Ringer 2/10 Write the objective
Read the article about Christmas lights and summarize (at least 5 sentences) how they work

3. Power & Energy in Electric Circuits Series Circuits

4. SERIES CIRCUIT
Only ONE current path if that is interrupted, the entire circuit won’t work.

5. SERIES CIRCUIT
Since only one path, current throughout the circuit is constant I = I1 = I2 = I3 = …

6. V = V1 + V2 + V3 +… SERIES CIRCUIT
Potential difference (V) across 2 points depends on the work needed to get between those 2 points V drops across each resistor (not constant)
V = V1 + V2 + V3 +…

7. SERIES CIRCUIT
Ohm’s law holds for each resistance
V = IR

8. Req = R1 + R2 + R3 + … SERIES CIRCUIT
Req = equivalent resistance of the system
Req = R1 + R2 + R3 + …

9. Example #1 Known V=9.0 V R1=2.0Ω R2=4.0Ω R3=5.0Ω R4=7.0Ω Unknown Req=I=

10. Example #2
We can find: Req = I = VR1= VR2= VR3=

11. SERIES CIRCUIT
Req = = 12 kΩ I = V/R = 1 mA VR1= IR1 = 3 V VR2= IR2 = 4 V VR3= IR3 = 5 V

12. Find: Req, I, VR1, VR2, VR3, VR4, VR5

13. Individual Practice
Complete #1-7 AND draw the corresponding circuits for #1-4

14. EXIT QUIZ

15. 1. What is the Req for this circuit?
The accompanying circuit diagram represents four resistors connected to a 12-volt source.
1. What is the Req for this circuit?
2. What is the total current in the circuit?
3. What is the voltage across R1?

16. Power in Electric Circuits
Rate at which energy is supplied to circuit
P = VI

17. Power = Current x Potential Difference Energy=Power x time
A 6.0-V battery delivers a 0.50-A current to an electric motor connected across its terminals
What power is delivered to the motor?
If the motor runs for 5.0 min, how much electric energy is delivered?

18. Example #2
The current through a light bulb connected across the terminals of a 125-V outlet is .50 A. At what rate does the bulb convert electric energy to light? (Assume 100 percent efficiency).

19. Practice Problems
A car battery causes a current of 2.0 A through a lamp and produces 12 V across it. What is the power used by the lamp?
What is the current through a 75-W light bulb that is connected to a 125-V outlet?
The current through the starter motor of a car is 210 A. If the battery maintains 12 V across the motor, how much electric energy is delivered to the starter in 10.0s?
A flashlight bulb is rated at .90 W. If the light bulb drops 3.0 V, how much current goes through it?

20. Energy Transfer Not all energy in a circuit is useful
Converted to heat (thermal energy)

21. Example:
Calculate the rate at which energy is supplied by a 120-volt source to a circuit if the current in the circuit is 5.5 amperes.

22. P = VI V I= R V2
P = R

23. Energy (W)
E = VIt
E = P t
E=I2Rt
V2t
E = R

24. Example:
How much energy is produced by a 50-volt source that generates a current of 5.0 amperes for 2.0 minutes?

25. Example:
An immersion heater has a resistance of 5.0 ohms while drawing a current of 3.0 amperes. How much electrical energy is delivered to the heater during 200. seconds of operation?

26. An operating 100. -watt lamp is connected to a 120-volt outlet
An operating 100.-watt lamp is connected to a 120-volt outlet. What is the total electrical energy used by the lamp in 60. seconds?