1. Circuit Test Mini-Review

2. For the following circuit: 20 Ω50 Ω 120 V

3. Circuit 1 Questions Is it series or parallel? What is the total resistance? What is the total current? What is the current through the 20 Ω resistor? How much power is dissipated by both resistors?

4. Label the following

5. What do you need to know? In a basic circuit (one battery, one resistor) To calculate Power? To figure out Resistance? To calculate Voltage? To find electric current?

6. For the following circuit:

7. Circuit 2 Questions Is it series or parallel? What is the total voltage? What is the voltage in each branch? What is the current in branch 1? ““““ in branch 2? ““ ““ in branch 3? What is the total current? What is the total resistance?

8. In your home… Are your plugs hooked up in series, or parallel? What device prevents your current from getting too high? If a lightbulb has a Power of 40 Watts, what is the resistance? (voltage in each plug is 120V)

9. Answers Slide 1 Series (only has one path) 70 Ohms (add up resistors in series) 1.7 Amps (I = V/R) 1.7 Amps (current is the same everywhere in the same path – constant in series) 205 W (Power = V*I)

10. Answers Slide 2 A. Resistor B. Switch C. Bulb D. Battery

11. Answers Slide 3 P = V * I R = V / I V= I * R I = V / R

12. Answers Slide 4 Parallel (multiple paths) 9V 9V (voltage is the same at each branch in parallel) 4.5 Amps, 3 Amps, 9 Amps, (I = V/R) I = 16.5 Amps (Add up all branch currents to find total current) R =.55 Ohms (R = V/I or 1/R = ½+1/3+1/1)

13. Answers Slide 5 Parallel (if you unplug one thing, everything else stays on. Constant voltage at each plug) Circuit Breaker (or Fusebox) 364 Ohms (P = V*I, R = V/ I) so 40 = 120 * I I =.33 Amps R = 120/.33 = 364 Ohms