OHMS law

Ohm's Law is written in one of the following forms.

  1. To work out Voltage use V = I x R
  2. To work out Current use I = V / R
  3. To work out Resistance use R = V / I

The units used are:

  • Voltage (in Volts) V
  • Current (in Amperes) A
  • Resistance (in Ohm's) Ω

NOTE:When people first used the Ohm (Ω) symbol in books it looked like 5r, (for 5 Ω) For the simple reason that people didn't have a ohm symbol on there typewriter.

I believe the best way to learn is to get stuck in so here's some examples.



What is V?
V = I x R
V = 1A x 100Ω
V = 100V


What is R?
R = V / I
R = 25V / 5A
R = 5Ω


What is I?
I = V / R
I = 10V / 200Ω
I = 0.05A

Always remember to work in the right units when working out Ohm's law calculations, you cant mix units e.g.(Volts, Ohm's and Milliamps.)

When working in electronics you will soon find that the Ampere and the Volt are rather large units, where the Ohm is very small, for this reason we can convert between multiples and submultiples (normally called the SI prefixes) of the basic units SI prefixes