Final answer:
The total resistance of resistors in series is found by summing their resistance values. For resistors in parallel, use the reciprocal formula to find the equivalent resistance, then add it to any series resistance present.
Step-by-step explanation:
To calculate the total resistance in a circuit, we must consider the configuration of the resistors. If resistors are in series, as in the third mentioned circuit, where R1, R2, and R3 are connected in series, we simply sum their resistances. The formula for total resistance (Rtot) of resistors in series is:
Rtot = R1 + R2 + R3.
For example, if R1 = 0.5 Ω, R2 = 7.5 Ω, and R3 = 11 Ω, the total series resistance would be:
Rtot = 0.5 Ω + 7.5 Ω + 11 Ω = 19 Ω.
For resistors in parallel, such as R2 and R3 in a different scenario, the total equivalent resistance (Rp) is found using the reciprocal formula:
1/Rp = 1/R2 + 1/R3
After calculating Rp, it would be added to any series resistance, like R1, to find the total resistance. This combination of series and parallel resistors suggests a mixed circuit which is often seen in physics problems about circuit analysis.