The Ultimate Guide to Electronics Formulas

Published on | 15 min read

A comprehensive guide to the fundamental formulas used in electronics, from Ohm's Law to series and parallel circuits, with detailed explanations and examples.

Ohm's Law

Ohm's law is the most fundamental formula in electronics, describing the relationship between voltage, current, and resistance.

Formulas:

  • V = I * R
  • I = V / R
  • R = V / I

Example: If a circuit has a 12V power source and a 100 Ohm resistor, the current flowing through the circuit is:

I = 12V / 100Ω = 0.12A

Power Law

The power law describes the relationship between power, voltage, and current.

Formulas:

  • P = V * I
  • P = I2 * R
  • P = V2 / R

Example: Using the previous example, the power dissipated by the resistor is:

P = 12V * 0.12A = 1.44W

Resistors in Series and Parallel

Series

Formula: R_total = R1 + R2 + ... + Rn

Example: Two resistors of 100Ω and 200Ω in series have a total resistance of 300Ω.

Parallel

Formula: 1 / R_total = 1 / R1 + 1 / R2 + ... + 1 / Rn

Example: The same two resistors in parallel have a total resistance of (100 * 200) / (100 + 200) = 66.67Ω.

Capacitors in Series and Parallel

Series

Formula: 1 / C_total = 1 / C1 + 1 / C2 + ... + 1 / Cn

Parallel

Formula: C_total = C1 + C2 + ... + Cn

Inductors in Series and Parallel

Series

Formula: L_total = L1 + L2 + ... + Ln

Parallel

Formula: 1 / L_total = 1 / L1 + 1 / L2 + ... + 1 / Ln

Related Articles

Frequently Asked Questions

A capacitor stores energy in an electric field, while an inductor stores energy in a magnetic field. Capacitors resist changes in voltage, while inductors resist changes in current.

In a series circuit, components are connected end-to-end, so the current flows through each component in turn. In a parallel circuit, components are connected across the same two points, so the current divides between them.

Reactance is the opposition of a circuit element to the flow of current due to that element's inductance or capacitance. A capacitor's reactance decreases with frequency, while an inductor's reactance increases with frequency.