3. http://phet.colorado.edu/new/simulations/sims.php?sim =Ohms_Law Voltage (Volts) Current (Amps) Resistance (Ohms or Ω)

5. What is the voltage of this battery? 4.5 V

6. Find the amount of resistance in a toaster oven that has a voltage of 120 V and has 3 amps of current running through it. Find the amount of resistance in a toaster oven that has a voltage of 120 V and has 3 amps of current running through it. I = V/R I = V/R 3amps = 120V/R 3amps = 120V/R R = 40 Ω R = 40 Ω

7. Find the voltage drop across each light bulb in the circuit below Find the voltage drop across each light bulb in the circuit below 10 V 1 Ω 2 V

8. Voltage will drop with each resistor. Voltage will drop with each resistor. The voltage will always drop to 0V in the end. The voltage will always drop to 0V in the end. 10 V 2 Ω

9. You must ADD the values of ALL resistors to find the total resistance for the circuit before you use Ohm’s Law You must ADD the values of ALL resistors to find the total resistance for the circuit before you use Ohm’s Law R T = R 1 + R 2 + R 3.. R T = R 1 + R 2 + R 3..

10. Your Turn… Find the amount of current in the circuit below Find the amount of current in the circuit below 10 V 2 Ω I = V/R T I = 1 amp

11. What is the current in each resistor? I = V/R T I = 9 / 3 I = 3 amps

12. For a parallel circuit, voltage drop over each resistor equals the total starting voltage For a parallel circuit, voltage drop over each resistor equals the total starting voltage 12 V 3 Ω

13. Practice!! What is the voltage drop over each light bulb? What is the voltage drop over each light bulb? What is the current over each? What is the current over each? 12 V 3 Ω 12 V 4 amps

14. In a parallel circuit, there are several paths for electrons to flow In a parallel circuit, there are several paths for electrons to flowSO…….. The current is divided equally among each branch of a parallel circuit The current is divided equally among each branch of a parallel circuit

15. Electrical Power P = IV Power (Watts) Current (Amps) Voltage (Volts)

16. Electric Companies We pay for electrical energy by the kilowatt-hour We pay for electrical energy by the kilowatt-hour Remember….. 1 Kilowatt = 1000 watts Remember….. 1 Kilowatt = 1000 watts

17. Def: Devices that measure or react to specific levels of current Def: Devices that measure or react to specific levels of current

18. Examples…… è è Safety Switches and Ground Fault Circuit Interrupters (GFCIs) designed to stop the flow of too much electricity

19. Examples…… è Fuse: è Fuse: contains a small piece of metal that melts if the current becomes too high, opening the circuit (must be replaced).

20. Examples…… è Circuit Breaker: è Circuit Breaker: contains a piece of metal that bends when it gets hot, causing a switch to open the circuit (can be switched back on).