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Level 3 Engineering Principles - DC Circuits Info and Equations

<br>https://engineers.academy/product/l3-nd-engineering-principles-exam-preparation/<br><br>Level 3 Engineering Principles - DC Circuits Info and Equations<br><br>

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Level 3 Engineering Principles - DC Circuits Info and Equations

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  1. LEVEL 3 ENGINEERING PRINCIPLES - DC CIRCUITS INFORMATION AND EQUATIONS Voltage, Current, Power and Resistance Subject Equation Variables and Units F =keq1q2 F = [attractive or repulsive] force in Newtons (N) Force between charged particles (Coulombs Law) r2 *1 Ke= Coulomb’s constant (Nm2C-2) I =Q *2 q = particle charge in Coulombs (C) Current Energy t r = distance between particles (m) I = Current in Amps (A) E = QV Q = [total] charge in Coulombs (C) R = ρL t = time in seconds (s) Resistance A E = energy in Joules (J) V = voltage in Volts (V) G = σA Conductance L R = resistance in Ohms (Ω) ρ = resistivity in Ohm-meters (Ωm) Change in Resistance (due to change in temperature) ΔR = RoαΔθ G = conductance in Siemens (S) σ = conductivity in Siemens per meter (S/m) Voltage (Ohm’s Law) V = IR A = cross section area of conductor in meters squared (m2) P = Et L = conductor length in meters (m) P = power in Watts (W) P = VI α = temperature coefficient of resistance (K-1) Power P = I2R θ = temperature in degrees Kelvin (K) P =V2 R Useful Constant Values: *1 Ke = 8.988 x 109 Nm2C-2 *2 qelectron = 1.603 x 10-19 C

  2. Resistor Colour Coding Example: Blue, Yellow, Orange, Red 6, 4, 103, 2% 64,000Ω = 64kΩ ± 2% 1 2 3 4 BAND 1 (digit 1) BAND 2 (digit 2) BAND 3 (multiplier) 100 101 102 103 104 105 106 107 108 109 10-1 10-2 BAND 4 (tolerance) COLOUR Black Brown Red Orange Yellow Green Blue Violet Grey White Gold Silver None 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 1% 2% 5% 10% 20%

  3. Resistors in Series and Parallel Subject Equation Variables and Units R = resistance in Ohms (Ω) V = voltage in Volts (V) I = Current in Amps (A) Total Resistance Resistors in Series: RT= R1+ R2+ R3 Supply Voltage Vs= V1+ V2+ V3 Supply Current Is= I1= I2= I3 Resistors in Parallel: 1 1 R1 1 R2 1 R3 Total Resistance = + + RT Supply Voltage Vs= V1= V2= V3 Supply Current Is= I1+ I2+ I3

  4. Capacitor Equations Subject Equation Variables and Units D = electric flux density in Coulombs per square meter (C/m2) D =Q Electric Flux Density (on Capacitor Plates) a Q = charge in Coulombs (C) C =Q a = capacitor common plate area in square meters (m2) V Capacitance C = capacitance in Farads (F) C = (a d)ε0εr V = voltage in Volts (V) d = distance between capacitor plates in meters (m) E =QV 2 *ε0 = absolute permittivity Energy Stored by a Capacitor εr = relative permittivity E =CV2 2 E = energy stored in Joules (J) τ = time constant in seconds (s) Capacitor Time Constant (Charging and Discharging through a Resistor) R = resistance in ohms (Ω) τ = RC Vc = voltage across capacitor (during charging) in volts (v) Vs = supply voltage in volts (v) −t τ) Capacitor Charging Voltage Vc= Vs(1 − e t = time under charge / discharge in seconds (s) Vd = voltage across capacitor (during discharging) in volts (v) Capacitor Discharging Voltage −t τ Vd= Vse Useful Constant Values: *ε0 = 8.85 x 10-12

  5. Capacitors in Series and Parallel Subject Equation Variables and Units C = capacitance in Farads (F) Q = charge in Coulombs (C) V = voltage in Volts (V) 1 CT 1 C1 +1 +1 Total Capacitors in Series: = Capacitance C2 C3 Total Charge QT= Q1= Q2= Q3 Supply Voltage Vs= V1+ V2+ V3 Capacitors in Parallel: Total CT= C1+ C2+ C3 Capacitance Total Charge QT= Q1+ Q2+ Q3 Supply Voltage Vs= V1= V2= V3

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