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Circuits and Electronics
Circuits
A circuit is a closed path through
which a continuous charge can flow.
 The path is provided by a lowresistance material, or conductor,
usually wire.
 Circuits are designed to do specific
jobs
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The Parts of a Circuit
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1. Voltage source – provides the electric potential for
charge to flow through the circuit.
2. Conductor – forms a connection from the voltage
source to the electronic device. Provides a closed
circuit.
3. Switch – part of a circuit designed to break the
closed path of charge.
4. Electrical device – any part of the circuit that
changes electrical energy into another form of energy.
(called a resistor)
Open and Closed Circuits
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If a circuit is open the charges cannot complete
their path and the flow is interrupted.
If a circuit is closed, the charges are able to
flow along the path and complete movement.
NOTE: When you turn a light switch to the
“ON” position, the path is closed and the lights
come on. When it is switched to the “OFF”
position it opens up the path and the charge
cannot flow; therefore the lights go out.
Current follows the path of least
resistance

Short circuit – an unintended path
connecting one part of a circuit
with another
 Follows a closed path, BUT not
the path that was intended.
Lamp connected to outlet…
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Functioning circuit
The charge flows through one wire through light bulb
and then back through the second wire to the outlet.
Short circuit
The cord has been damaged and the two wires inside
have formed a connection. Now the path of least
resistance is through one wire and back through the
second wire. This leads to too much current in wire
which can lead to shock in humans or can create a
fire.
Danger! Danger!
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Too much current in a circuit is dangerous.
Safety devices are built into outlets that will
open up the path at the outlet preventing the
flow of charges.
This is to prevent danger to humans and to
prevent fires from being started.