Equations
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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)