1. CIRCUITS AND RESISTANCE

2. RECALL: CurrentPotential Difference Definition The flow of electronsCauses electrons to flow SymbolIV UnitsAmps (A)Volts (V) Formula (if applicable) I = Q t V = E Q How measured (if applicable)AmmeterVoltmeter

3. Circuits: A circuit is made up of a power supply, connecting wires & various elements that allow electrons to leave a power source, travel through the elements & return back to the power source.

4. Common Electric Symbols Battery/Power Source Bulb

5. Common symbols (cont’d) Switch Push-button Switch Resistor Voltmeter Ammeter VA

6. Circuits Power Supply Resistor A Ammeter v Voltmeter

7. Types of Circuits:  There are 2 types of circuits:  1.Series Circuit  2.Parallel Circuit SERIES Trick to help identify type of circuit: Series:Pen follows wire Parallel: Pen can go in more than one direction PARALLEL

8. Series or Parallel? A A SERIES PARALLEL 1. 4.3. 2.

9. Symbol: R Units:Ohms, Ω Resistance Resistance is how difficult it is for current to flow A device with HIGH Resistance will have very little current passing through it A device with low resistance will have a large current passing through it A resistor is used to slow current down

10. IF: R is High than I is low R is Low than I is h igh

11. Equivalent Resistance - Req  Equivalent Resistance is the TOTAL resistance of a circuit Symbol: Req Units:Ohms = Ω  Formulae: Series: Req = R 1 + R 2 + R 3 + … Parallel:

12. 5  3  10  Type of circuit:Series Formula:Req = R 1 + R 2 + R 3 R eq = 10 + 5 + 3 R eq = 18  What is the equivalent resistance (Req) of the circuit below?

13. 30  75  Type of circuit:Series Formula:Req = R 1 + R 2 R eq = 75 +30 R eq = 105  What is the equivalent resistance (Req) of the circuit below?

14. Type of circuit: Parallel Formula: What is the equivalent resistance (Req) of the circuit below? 10 Ω 15 Ω 1 ÷ 0.1666 = 6Ω

15. Type of circuit: Parallel Formula: What is the equivalent resistance (Req) of the circuit below? 1 ÷ 0.3333 = 3Ω 15  5  15 

16. KEY POINTS  Symbols of circuit parts: Voltmeter, Ammeter, Power Supply, Resistor  Two types of circuits (series and parallel)  Formula for Req (equivalent resistance) Series – Req = R 1 + R 2 + R 3 Parallel -

17. RECALL: ResistanceCurrentPotential Difference Definition Slows current down The flow of electrons Causes electrons to flow SymbolRIV Units Ohms (Ω) Amps (A)Volts (V) Formula (if applicable) R = V I I = Q t V = E Q How measured (if applicable)CalculatedAmmeterVoltmeter