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Ohm’s Law & Circuits
Chapter 7.2 & 7.3
Flow of Charge
• Electricity (charge)
– Flow of electrons
– Caused by differences
in charge
• Charge will flow from
negative to positive
end
Electric Current
• Rate the electrons are moving
• Conductors have electrons that are free to move
– Measured in amperes (A)
Voltage
• Provides “electric pressure” (force per area) to
move electrons between two terminals in a
circuit
• Causes current
• Measured in volts (V)
Electric Resistance
• Resists to the flow of charge
– Measured in Ohms (Ω)
Ohm’s Law
• Current= voltage
resistance
The greater the
resistance, the less
the current
The greater the voltage,
the greater the
current
Source of Electrons in a Circuit
• Source of electrons does not come from a
power outlet but from the conducting circuit
material (wires)
– Energy flows from outlets to the circuit causing
electrons to move
Circuit
• Complete path from a positive to negative
terminal of a battery
– Electrons flow from the negative to positive end
Parts of a circuit
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•
Battery
Closed switch (allows electrons to flow)
Open switch (impedes flow)
Wire
Resistor
Light Bulb
Types of circuits
• Depend on how more than one device receive
electrical energy
– Series
• Single pathway of electron flow
– Parallel
• Branched pathway, each of which is separate path for
the flow of electrons
Disadvantages of Series Circuits
• If one device fails, it causes an open circuit
where no current can flow