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Electric circuits
1 volt = 1 joule per coulomb
1 ampere = 1 coulomb per second
Some terms
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Ampere
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Rate of current flow (coulombs/second)
What is current flow in a circuit?
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Electron flow? Very slow!
Why is current established instantly?
Voltage-current analogy: water flowing in
a pipe because of pressure
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Electrical resistance (“load”)
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resistance ~ friction
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Produces heat –
just like friction!
Voltage, current
and resistance
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current =
Voltage produces
current
Resistance reduces
current
voltage
resistance
A=
V
Ω
Ohm’s Law
Electrical shocks
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Current produced by difference in
voltage
Touching two different voltage sources
causes current to flow, depending on
the voltage difference
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This is similar to but not the same as
sparking, caused by a buildup of charge
on your body
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Electric circuits
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A circuit is a complete pathway along
which current can flow
A voltage must be present for current
to flow in the circuit
Work can be done by the current if
loads are placed in the circuit
Series circuits
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V=A×Ω
Loads connected one after the other
Resistance is the sum of the loads
If one load fails, the circuit is broken!
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Parallel circuits
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V=A×Ω
Loads are connected alongside each other
Current is the sum of the branches
Total resistance falls as loads are added!
Why parallel circuits are
dangerous
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The more parallel
loads, the more
current flows
The more current
flows, the heat is
generated in the
feed wires
Eventually, the
wires will melt…
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