Resistance
Resistance is the opposition offered by a conductor to the flow of current. R = V/I. Unit is the ohm (Ω).
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Definition of resistance
The resistance R of a conductor is the ratio of the potential difference V across it to the current I through it: R = V/I. The SI unit is the ohm (Ω). Higher resistance means less current for a given voltage. Resistors are components designed to have a specific resistance.
Resistors in series and parallel
In series: total resistance R_total = R₁ + R₂ + … . In parallel: 1/R_total = 1/R₁ + 1/R₂ + … . These rules allow us to simplify circuits and find current and voltage in each part.
Why resistance matters
Resistance limits current and causes a drop in potential (V = IR). It also leads to heating (Joule heating: P = I²R). Understanding resistance is essential for designing and analysing electric circuits.
Why does adding a resistor in parallel reduce the total resistance, while adding one in series increases it?