2. Ohms Law

The relationship between Voltage, Current and Resistance in any DC electrical circuit was firstly discovered by the German physicist Georg Ohm, (1787 - 1854). Georg Ohm found that, at a constant temperature, the electrical current flowing through a fixed linear resistance is directly proportional to the voltage applied across it, and also inversely proportional to the resistance. This relationship between the Voltage, Current and Resistance forms the bases of Ohms Law and is shown below.

a. Ohms Law Relationship

By knowing any two values of the Voltage, Current or Resistance quantities we can use Ohms Law to find the third missing value. Ohms Law is used extensively in electronics formulas and calculations so it is "very important to understand and accurately remember these formulas".

[V = I x R]      V (volts)  = I (amps) x R (Ω)

[I = V ÷ R]      I (amps)  = V (volts) ÷ R (Ω)

[R = V ÷ I]      R  (Ω) = V (volts) ÷ I (amps)

It is sometimes easier to remember Ohms law relationship by using pictures. Here the three quantities have been superimposed into a triangle giving voltage at the top with current and resistance at the bottom. This arrangement represents the position of each quantity in the ohm's law formulas.

b. Ohms Law Triangle

Next topic will be on Resistor