Final answer:
The equivalent resistance between points a and b in a circuit depends on whether the resistors are in series or parallel, using simple addition for series or a specific formula for parallel resistors: Req = (R₁ * R₂) / (R₁ + R₂).
Step-by-step explanation:
To calculate the equivalent resistance (Rab) between points a and b in a circuit, different rules are applied depending on whether the resistors are in series or in parallel. For resistors in series, the equivalent resistance is simply the sum of the individual resistances. In contrast, for resistors in parallel, the equivalent resistance is found using the formula 1/Req = 1/R₁ + 1/R₂ for two resistors. When multiple resistors are involved, the process may require breaking down the circuit into simpler series and parallel combinations, calculating the equivalent resistance for each combination, and then adding them together if they are in series or applying the parallel resistance formula if they are in parallel.
The formula for the equivalent resistance of two parallel resistors R₁ and R₂ is Req = (R₁ * R₂) / (R₁ + R₂). To find the equivalent resistance in more complex circuits, it may be necessary to progressively reduce the circuit by combining resistors in series and parallel until a single equivalent resistance is found.