CIRCUITS AND RESISTANCE
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
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.
Common Electric Symbols Battery/Power Source Bulb
Common symbols (cont’d) Switch Push-button Switch Resistor Voltmeter Ammeter VA
Circuits Power Supply Resistor A Ammeter v Voltmeter
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
Series or Parallel? A A SERIES PARALLEL
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
IF: R is High than I is low R is Low than I is h igh
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:
5 3 10 Type of circuit:Series Formula:Req = R 1 + R 2 + R 3 R eq = R eq = 18 What is the equivalent resistance (Req) of the circuit below?
30 75 Type of circuit:Series Formula:Req = R 1 + R 2 R eq = R eq = 105 What is the equivalent resistance (Req) of the circuit below?
Type of circuit: Parallel Formula: What is the equivalent resistance (Req) of the circuit below? 10 Ω 15 Ω 1 ÷ = 6Ω
Type of circuit: Parallel Formula: What is the equivalent resistance (Req) of the circuit below? 1 ÷ = 3Ω 15 5 15
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 -
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