Equations Flashcards
What are the three equations that can be used to determine the Voltage in any given circuit?
I.R
(current x resistance)
P/I
(power / current)
√P.R
(square root of power x resistance)
What are the three equations that can be used to determine the Current in any given circuit?
V/R
(voltage / resistance)
P/V
(power / voltage)
√P/R
(square root of power / resistance)
What are the three equations that can be used to determine the Resistance in any given circuit?
V/I
(voltage / current)
V²/P
(voltage squared / power)
P/I²
(power / current squared)
What are the three formulae that can be used to determine the Power in any given circuit?
V.I
(voltage x current)
I².R
(current squared x resistance)
V²/R
(voltage squared / resistance)
What is the equation for calculating the total resistance (Rₜ) in a circuit with two resistors in paralell?
Rₜ = R₁xR₂ / R₁+R₂
What is the equation for calculating the total resistance (Rₜ) in a circuit with more than two resistors in paralell?
1/Rₜ = 1/R₁ + 1/R₂ + 1/R₃ … etc.
What is the equation for calculating the total resistance (Rₜ) in a circuit with more than one resistors in series?
Rₜ = R₁ + R₂ + R₃ + R₄ …etc
What is the formula for Kirchoff’s Law regarding voltage (Vₜ) in a paralell or series circuit?
Vₜ = V₁ + V₂ + V₃ + V₄ …etc
What is the formula for Kirchoff’s Law regarding current (Iₜ) in a paralell or series circuit?
Iₜ = I₁ + I₂ + I₃ + I₄ …etc.
Briefly describe Kirchoff’s voltage law (KVL).
“the sum of the voltage differences around any closed loop in a circuit must be zero”
Basically, all of the voltage that goes into a circuit must be accounted for at the end of the circuit.
Briefly describe Kirchoff’s Current law.
“the current flowing into a node (or junction) must be equal to the current flowing out of it”.
Basically, all of the current that flows into a component of a circuit must also flow out of it in a closed circuit loop.
What is the formulae that can be used to determine the resistivity (R) of a conductor?
What two other mathmatical expressions can be used to signify the relationship between resistivity and the other factors governing cable choice?
R = P x l / a
(resistivity = rho x length / area)
R ∝ l
(resistivity is proportional to length)
R ∝ 1/a
(resistivity is inversly proportional to area)
P = Rho
l = Length
a = cross sectional area
What are the two equations that can be used to work out the quantity of Charge (Q) in a circuit?
Q = I.t
(charge = current x time in seconds)
Q = V.C
(charge = voltage x coulombs)
What is the formula for calculating the total capacitance (Cₜ) of a circuit in series?
Cₜ = C₁ + C₂ + C₃ + C₄ …etc
What is the formula for calculating the total capacitance (Cₜ) of a circuit in paralell?
1/Cₜ = 1/C₁ + 1/C₂ + 1/C₃ + 1/C₄ …etc.
What is the formula for efficiency?
How is the result of the equation presented?
Efficiency = output power / inputpower
It is presented as a percentage.
What is the formula used to calculate the energy (J) in a magnetic field?
1/2.L.I²
(0.5 x inductance in henrys x current squared)
What is the equation used to calculate the force required to move an object that is accelerating at any given speed?
F = m.a
(Force = mass x acceleration)
What is the equation used to calculate the acceleration of an object?
a = d/t²
(Acceleration = distance / time²)
What is the equation used to calculate the average acceleration of any given object?
Av. a = avg. v / t
(Average acceleration = average velocity / time)
What is the equation used to calculate the force required to move an object?
F = m.a
(Force = mass x acceleration)
What is the equation used to calculate work done?
W = F.d
(Work = force x distance)
Force requires the weight of an object (ie. the mass x the acceleration due to gravity)
How do you calculate the weight (w) of an object?
w = m.g
(Weight = mass x acceleration due to gravity - 9.81)
What equation is used to calculate the power (P) of a process?
P = W/t
(Power = work done / time taken)
