Transcript Electric Circuits and terms

Electric Circuits and terms
Electric circuits move charges around to
deliver energy
Electric Circuits
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Charges move when there is a difference in electric
Potential. Electric Potential (think of potential
energy) is called electric Voltage
Voltage is the driving energy for a circuit and it
causes charges to move around.
Charges move around and deliver energy (charges
are like the tennis balls, these tennis balls (charges)
carry energy (volts) which can be delivered to
something in the circuit (like a light bulb)
The movement or flow of charges is called electric
current (coulombs/sec = amps)
Current is measured in amps, the symbol for
current is I.
Electric Circuit
Simple circuit
Electric Current
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The amount of electric current depends on
the amount of Voltage applied (think of the
amount of energy available) and depends on
the resistance in the circuit
For circuits we often use the analogy of
flowing water. Voltage = water pressure,
current = flow rate, and resistance is the size
of the pipe (or friction in the pipe)
Electric circuits
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Resistance is measured in Ohms.
Light bulbs, toasters, hair dryers, etc. and
basically just resistors which use up energy.
Ohms law : relates how much current flows in
a circuit.
Ohms law: V = I x R, Voltage = current x
resistance.
Ohm’s law: V = I x R
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Example: How much current (I = amps) does
a lightbulb (R = 20 ohms) use when
connected to 120V (typical voltage in your
house)?
V = I x R , or I = V/R = 120V/20ohms =
6amps
Electric Power
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Lightbulbs are rated in power units = watts.
Power = energy per time.
For electric circuits, P = V x I.
Summarize circuit terms
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Voltage: This is the amount of electical energy
supplied. Charges carry around energy and transfer
this to things like lightbulbs.
Current: This is the flow of charges or how many
charges flow per second. Measured in
Coulombs/sec = Amp (symbol is I)
Resistance: A light bulb acts like a resistor which
uses up energy
Ohm’s law (relates the above 3 terms: V = I R) or
Voltage = Current x Resistance.
Electric Circuits
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V(volts) = I(current) x R (resistance)
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P (power) = V x I = V2 / R = I2 x R
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P = power =energy/time = joules/sec = watts
I = current = coulombs/sec = amps
R = resistance = ohms
V = Volts (energy) = joules/coulomb
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