Basic electronic formulas

  • Series components have the same amount of current flowing through them.
  • Parallel components have the same voltage across them.
  • Kirchhoff’s laws
    • Voltage: Supply voltage is split up among series components.
    • Current: The amount of current flowing through each series component is the same.

Ohms law.

One amp (A) of current (I) will flow through one ohm (Ω) of resistance (R) when one volt (V) is across that resistance. That is the basis for ohms law. Voltage (V) is the electric potential, or energy, to move charges. Current is the flow of charges. Whereas resistance is the amount of opposition to charges flowing though it.

  • I = V/R
  • R = V/I
  • V = IR

Current is voltage divided by resistance.

Resistance is voltage divided by current.

Voltage is current times resistance.

A perfect conductor would have no resistance. They don’t exist, but most of the time, the wires and other connectors in circuits usually have so little resistance that it is not added into the Ohms law calculations.

A perfect insulator would have infinite resistance. They also do not exist, but most insulating material has so much resistance that it’s safe to just assume that it is infinite in almost all calculations.

Examples of how Ohms law can be used: (pages still being added)

  • Calculating current. Examples will be added to a dedicated page.
    • Current through a certain value resistor.
    • Current through an LED of a certain voltage in series with a certain value protective resistor.
    • Series resistors.
    • Parallel resistors.
  • Calculating resistance. Examples will be added to a dedicated page.
    • Battery internal resistance.
  • Calculating voltage. Examples will be added to a dedicated page.

To be added


  • Power/Wattage. Many possible formulas.
  • Diode drops.
  • Voltage divider.
  • Capacitance/Farad.
  • RC Time Constant.
    • Monostable 555
    • Astable 555
  • Voltage ramp/Op amp integrator.

Good topics to check out next:

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