How is total resistance calculated in a parallel circuit?

• A. RT = IR1 + IR2
• B. RT = 1/(1/R1 + 1/R2)
• C. RT = VR1 + VR2 + VR3
• D. RT = IR1 = IR2

Answer: (B)

In a parallel circuit, the total resistance is calculated using the formula that involves taking the reciprocal of the sum of the reciprocals of the individual resistances. This approach reflects how current divides among the parallel branches.

When resistors are connected in parallel, the voltage across each resistor is the same, allowing the calculation of total current from the individual currents flowing through each resistor. The formula RT = 1/(1/R1 + 1/R2) effectively combines these individual resistances to yield a total resistance that is less than any of the individual resistances. This means that as more resistors are added in parallel, the total resistance decreases, reflecting the increased pathways for current flow.

The other options either do not apply the principles of parallel circuits correctly or represent different concepts altogether. For instance, simply adding the currents or voltages does not accurately reflect the relationships in a parallel circuit, hence affirming the importance of the specific formula for total resistance in this configuration.