Capper Shaw Electrical - Warrington

Use the calculator below to work out the Voltage, Current or Resistance based on the known values. Where Current = Voltage / Resistance.

 

Ohms Law Explanation

1) A basic electrical circuit has three components

Voltage (V)

Amperes (A)

Resistance (Ω)

2) Ohms law states that these 3 components are always related in the same way mathematically

They are related as follows

• V = I x R (Volts = Amps x Resistance)

• I = V / R (Amps = Volts / Resistance)

• R = V / I (Resistance = Volts / Amps)

The above triangle is the easiest way to remember this relationship. If you cover with your finger the figure you want to work out, what's left is the sum you need to do. (Note If you cover a letter from the bottom, also cover the x symbol as well.)

• Cover over 'I' and you are left with 'V' over 'R' or the sum V / R

• Cover over 'V' and you are left with 'I' x 'R'

• Cover over R and you are left with V / I

Now if we replace the letters with numbers we can calculate the number for the part of the circuit that is missing. Here are some worked examples.

If you want to know V and you know I = 4 and R = 2 here's the sum

V = I x R

V = 4 x 2

V= 8

To know R when V = 8 and I = 4 here's the sum

R= V / I

R = 8 / 4

R = 2