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2.4. Series & Parallel Circuits. Circuit Diagrams. A practical way to describe a circuit is to draw a circuit diagram Uses standard symbols to represent the components and their connections. You Try!. Draw a simple circuit (using symbols) that includes: 2 cells A switch A resistor
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2.4 Series & Parallel Circuits
Circuit Diagrams • A practical way to describe a circuit is to draw a circuit diagram • Uses standard symbols to represent the components and their connections
You Try! • Draw a simple circuit (using symbols) that includes: • 2 cells • A switch • A resistor • A light bulb
Types of Circuits • There are essentially 2 types of circuits: • Series • Parallel
Series Circuits • Only 1 pathway for current to flow • Simple • Electrons only have one path to follow • Each electron must go through each load, in turn • Current (I) is the same at each point in the circuit
Parallel Circuits • More than 1 pathway for current to flow • Charges flow around 2 or more different “loops” • Current is not the same at all points • Some electrons will take one path and others will take a different path • Most circuits are a combination of series and parallel
Ammeters • Ammeter measures current (in amperes, A) at a particular location in the circuit • Where the ammeter is located! Ammeter is always connected in series
Voltmeters • Voltmeter measures potential difference (in volts, V) between 2 points • Electric potential on one side of a load, such as a bulb or resistor, is greater than the electric potential on the other side • Voltmeter measures this difference Always connected in parallel
Back to this guy… • What if one of the bulbs was burnt out? • Bulbs must be connected in parallel • How do we turn the lights on? • 1 switch • Power source and switch must be connected in series
Loads in Series – Current (I) • The current is the same at all points in a series circuit • IT = I1 = I2 = I3…
Loads in Series – Potential Difference (V) • Loads transform electrical energy into other forms of energy • The total energy transformed must equal the work that is done by the cell (power source) • .: The potential difference of the cell must equal the sum of the potential differences of each load
Loads in Series – Potential Difference (V) • VT = V1 + V2 + V3 …
Loads in Series – Resistance (R) • The total resistance of the circuit will increase as more loads are added in series • RT = R1 + R2 + R3… • What would happen if we added more loads (i.e. light bulbs) in series?
Loads in Parallel – Current (I) • There is more than one path for electrons to flow • The current entering a parallel connection divides • The sum of the currents through each path equals the total current • IT = I1 + I2 + I3 …
Loads in Parallel – Potential Difference (V) • Voltage is the same across all loads in the circuit • Equivalent to the potential difference across the cell • VT = V1 = V2 = V3…
Loads in Parallel – Resistance (R) • The total resistance of loads connected in parallel, is less than the resistance of any of the loads individually • RT < R1; RT < R2; RT < R3; …