Which of the following is a formula for calculating total resistance in a parallel circuit?

In a parallel circuit, the total resistance is calculated using the formula RT = 1/(1/R1 + 1/R2 + 1/R3). This approach is based on the principle that in a parallel configuration, the voltage across each resistor is the same, and the total current is the sum of the currents through each individual resistor.

This formula arises from the reciprocal nature of the resistances in parallel. Each term (1/R1, 1/R2, etc.) represents the conductance of each resistor. When you add these reciprocal values together, you effectively find the total conductance of the circuit. Taking the reciprocal of this sum gives you the total resistance.

This formula is crucial in determining how resistors behave in parallel, allowing you to understand how they share the total current and affect the overall resistance of the circuit. Thus, option C accurately describes the correct method for calculating total resistance in a parallel circuit.