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Diagramming circuits
Ohm’s Law Mnemonic
Definitions
Current: the number of electrons that go
through a wire in one second
Voltage: the pressure that pushes the
electrons
V = IR
R = V/I
I = V/R
Resistance: the material property that
makes it hard to push an electron through a
wire
Power: the rate at which energy is used up.
The more power, the brighter a light bulb.
Ohm’s Law Mnemonic
P = IV where
P = Power (in Watts, the rate at which energy is consumed)
I = Current
V = Voltage
Typical household voltage is 120V.
Important equations for Electricity
Series Circuits
VT = V 1 + V 2 + V3 + …
RT = R1 + R2 + R3 + …
IT = I 1 = I 2 = I 3 = …
V = Voltage (Volts)
I = Current (Amps)
R = Resistance (Ohms)
In a series electric circuit all of the electrons
must flow through the same elements.
Parallel Circuits
VT = V 1 = V 2 = V3 = …
1/RT = 1/R1 + 1/R2 + 1/R3, …
IT = I 1 + I 2 + I3 + …
In a series circuit each resistor adds to the total
resistance.
In a parallel electric circuit electrons may flow
through different circuit elements.
In a parallel circuit each resistor provides
another way for electrons to flow.
Series Circuit
I4 =
A
VT = V1 + V2 + V3 + …
V
V7 =3
R7 =
V
V8 =
R8 = 2
RT = R1 + R2 + R3 + …
V6 = 5
+
A I5 =
IT = I 1 = I 2 = I 3 = …
Parallel Circuit
R1 =
100 Ohms
R2 =
200 Ohms
VT =
V1 =
V2 =
RT =
VT
+
R1
IT
IT =
I1 =
I2 = 0.4A
A
V1, I1
R2
V2, I2
V
Parallel Circuit
R1 =
200 Ohms
R2 =
200 Ohms
VT =
V1 =
V2 =
RT =
VT
R1
IT
IT =
I1 =
I2 = 1A
A
V1, I1
R2
V2, I2
V