“Ohms Law states that a voltage, V across a resistor, R is directly proportional to the current, I flowing through the same resistor”
The relationship between Voltage, Current and Resistance in any DC electrical circuit was firstly discovered by the German physicist Georg Ohm. 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.
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”.
To find the Voltage, ( V )
[ V = I x R ] V (volts) = I (amps) x R ( W )
To find the Current, ( I )
[ I = V ÷ R ] I (amps) = V (volts) ÷ R ( W )
To find the Resistance, ( R )
[ R = V ÷ I ] R ( W ) = V (volts) ÷ I (amps)
A resistor (or resistance) which obeys the above rules of Ohm’s law is known as a linear resistor. Linear resistors have a constant resistance for all values of positive or negative voltages and currents. This linear relationship gives a current-voltage ( I-V ) characteristic of a straight line. A nonlinear resistor does not obey Ohm’s law and will therefore have a non-straight I-V curve.