How is total resistance (RT) calculated in a parallel circuit?

In a parallel circuit, the total resistance can be found by applying the formula for resistors in parallel: the sum of the reciprocals of the individual resistances is equal to the reciprocal of the total resistance. This relationship acknowledges that in a parallel configuration, the voltage across each resistor is the same, and the total current flowing through the circuit is the sum of the currents through each resistor. The correct formula is given by:

1/RT = 1/R1 + 1/R2 + ... + 1/Rn

This formula demonstrates that the total resistance decreases as additional pathways for current flow are introduced, contributing to a lower equivalent resistance than that of the smallest resistor in the group. Hence, selecting the option that states 1/R1 + 1/R2 correctly captures this principle, allowing us to calculate the total resistance effectively.

In contrast, the options that sum the resistances directly (like adding R1 + R2) or involve subtraction would apply to series circuits, where resistances add up directly without affecting the identified pattern of current flow that is found in parallel circuits. Additionally, the option that involves multiplying resistances over their sum pertains to solving for two resistors in parallel but is not the complete formula necessary for three or