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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 - PowerPoint PPT Presentation
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Series & Parallel Circuits
2.4
Circuit DiagramsA practical way to describe a circuit is
to draw a circuit diagram
Uses standard symbols to represent the components and their connections
SYMBOL COMPONENT
SYMBOL COMPONENT
Connecting wire
Cell
Switch Battery
SYMBOL COMPONENT
SYMBOL COMPONENT
Resistor Voltmeter
Bulb Ammeter
You Try!
Draw a simple circuit (using symbols) that includes: 2 cells A switch A resistor A light bulb
What’s happening here?
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; …