Basic Electronic Formula

Ohms Law

• The relationship between voltage, current and resistance in a circuiit is defined by Ohms law...
  • E = I x R, Electromotive force = Current multiplied by Resistance.
• to find the other two values a simple transposition applies...
  • I = E/R.
  • R = E/I

Resistors in series

• Rt = R1 + R2 + R3 +...Rn

Resistors in parallel

• Rt = 1/(1/R1 + 1/R2 + 1/R3 +...1/Rn).
• For two resistors in parallel it is a little simpler...
  • Rt = (R1 x R2) / (R1 + R2).

Capacitors in series

• Ct = 1/(1/C1 + 1/C2 + 1/C3 +...1/Cn).
• For two capacitors in parallel it is a little simpler...
  • Ct = (C1 x C2) / (C1 + C2).

Capacitors in parallel

• Ct = C1 + C2 + C3 +...Cn

NOTE...
You may have noticed that the formula for capacitors is the opposite to the formulas for resistors!

Power dissipated by a circuit

• When a current passes theough a component, energy is given off in the form of heat.
  • W= E x I, Watts = Electromotive force x Current.

• As with resistors a simple transposition finds the other two values...
  • E = W/I
  • I = W/E

Inductors in series

• Lt = L1 + L2 + L3 +...Ln

Inductors in parallel

• Lt = 1/(1/L1 + 1/L2 + 1/L3 +...1/Ln).
• For two resistors in parallel it is a little simpler...
  • Lt = (L1 x L2) / (L1 + L2).