Resistors and Resistance

Resistors in Series
For resistors in series the total resistance can be calculated using the following equation:

R = R1 + R2

Each series resistors has the same value for the current and the potential difference across each resistor add up to give the total voltage.

Resistors in Parallel
For resistors in parallel the total resistance can be calculated using the following equation.



For each resistors in parallel the potential difference between them is the same, however the currents add up to give the total current in the circuit.

 

 

Resistivity
Unlike resistance, resistivity is a set value, which does not change regardless of the area or length of a material and is therefore particularly useful in engineering.

Definition
Numerically equal to the resistance of a one meter length of material with a cross-sectional area of 1m2.

Equation

Where
= Resistivity (m)
R = Resistance ()
V = Potential Difference (V)
L = Length (m)