1. Circuits 6.3

2. Series Circuits  Electric circuit with only one branch.  Used in things such as flashlights and lamps  Amount of current is the same in all parts  If a part is disconnected, the circuit is broken  Light doesn’t light up  Open circuits  If part of the circuit is removed, the circuit is open  Current does not flow, and object does not work

3. Parallel Circuits  Circuits that have 2 or more branches  Current can go through any number of the branches  You can turn lights off in one room, and not kill power for whole house  Used in homes for this reason  Circuit breakers protect against overheating wires  Flips open if the wire gets too hot, stopping the circuit  Fuses do a similar thing  Fuses contain a metal that melts if too much current passes through

4. Electrical Power and Energy  Electrical Power=Rate at which electrical energy is converted to another form  P=IV  Electrical Power (W)=current(A) x voltage difference (V)  Measured in kilowatts (kW)  1kW=1000W

5. Example Problem  The current in a cloths dryer is 15 A when it is plugged into a 240 V outlet. What is the power of the cloths dryer? Answer in kW.  K: I=15A V=240V  U: P=?  E: P=IV  P=IV=(15A)(240V)  =3600W  =3.6kW

6. Guided Practice  If a blender is plugged into a 120 V outlet that supplies 2 A of current, what amount of power is used by the blender?

7. You Try It!  If a clock expends 3 W of power from a 1.5 V battery, what amount of current is supplying the clock?

8. Calculating Electrical Energy  E=Pt  Electrical energy (kWh)=electrical power (kW) x time (h)  To figure out cost for electricity, Power Companies, such as Xcel, multiply kWh by cost per kWh.  Currently the average in the U.S. is $0.10 per kWh.  Mine was $0.07 per kWh last month.

9. Example Problem  A microwave with a power rating of 1200 W is used for 15 minutes. How much electrical energy did the power company provide for the microwave?  K: P=1200Wt=15 minutes  U: E=?  Need to convert!  P=1200W (1kW/1000W)=1.2kW  T=15 m (1hr/60min)=0.25h  E=  (1.2kW)(.25h)=0.3kWh

10. Guided Practice  A TV plugged into a standard U.S, outlet has a current of 10 A through it. If a football game took 3 hours, how much did the game cost to watch assuming the electric company charges $0.10 per kWh?

11. You Try it!  A current of 15 A runs through an appliance with resistance of 3Ω. The appliance runs 24 hours a day. If the cost per kWh is $0.10, what is the daily cost to run the appliance?