# Total Resistance

• “Total Resistance” in an electrical circuit refers to the sum of all individual resistance values from each separate component within the circuit.

• It’s measured in ohms (Ω), named after German physicist Georg Simon Ohm whose Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

• In series circuits, total resistance (Rt) is computed by adding all the individual resistances together (R1+R2+…+Rn).

• In parallel circuits, calculating total resistance is more complicated. The formula used is 1/Rt = 1/R1 + 1/R2 +…+ 1/Rn.

• Greater total resistance decreases the current flow in the circuit, as more energy is required to push the electric charges through higher resistance.

• High total resistance can limit the functionality of a circuit. For instance, if resistance is too high, a light bulb in the circuit might not receive enough current to glow.

• In practical applications, the concept of total resistance is important in designing circuits and understanding the distribution of electrical power in complex circuits.

• Factors that influence resistance include the type and thickness of the material, the length of the conductor and its temperature.

• Lastly, remember to identify whether a circuit is a series or parallel when calculating total resistance. In the exam, sketching a simple diagram may help visualise the circuit.