Electrical quantities Flashcards
Formulas involving electricity
What is the formula for
Current
I = Q / t
current = charge / time
A = C / s
What is the formula for
Resistance
R = V / I
resistance = potential difference / current
Ω = V / A
What is the formula for
Power
(Using current and voltage)
P = IV
power = current × voltage
W = A × V
What is the formula for
Energy transformed
E = IVt
energy transformed = current × voltage × time
J = A × V × s
What is the formula for
Resistance in series circuits
R = R₁ + R₂ + … + Rₙ
combined resistance = sum of the resistances
Ω = Ω + Ω + … + Ω
What is the formula for
Voltage in series circuits
V = V₁ + V₂ + … + Vₙ
total voltage = sum of voltage drops across resistors
V = V + V + … + V
What is the formula for
Current in series circuits
I = I₁ = I₂ = … = Iₙ
The current doesn’t change across a series circuit.
A = A = A = … = A
What is the formula for
Resistance in parallel circuits
1 / R = 1 / R₁ + 1 / R₂ + … + 1 / Rₙ
reciprocal of combined resistance = sum of the reciprocals of resistances
1/Ω = 1/Ω + 1/Ω + … + 1/Ω
What is the formula for
Voltage in parallel circuits
V = V₁ = V₂ = … = Vₙ
The voltage doesn’t change across a parallel circuit.
V = V = V = … = V
What is the formula for
Current in parallel circuits
I = I₁ + I₂ + … + Iₙ
total current = sum of current across resistors
A = A + A + … + A
What is the
Transformer equation
Vₚ / Vₛ = Nₚ / Nₛ
voltage across primary coil / voltage across secondary coil
= number of turns on primary / number of turns on secondary
V / V = n / n
What is the
Equation relating the primary and secondary voltages
Iₚ × Vₚ = Iₛ × Vₛ
power in to primary coil = power out of secondary coil
A × V = A × V
