What is the formula used to calculate the resistance of a certain length of a conductor?

The formula for calculating the resistance of a certain length of a conductor is based on the relationship between resistance, the length of the conductor, and its specific resistance (or resistivity). The correct formula incorporates the direct proportion between resistance and length while simultaneously accounting for the unit of measure used.

For conductors, the resistance (R) can often be expressed as directly proportional to the length (L) of the conductor and the resistivity value (DC Res). In this case, the formula shows that the resistance increases with length. The division by 1000 indicates that the length is measured in meters while the resistivity is expressed in ohm-meters, which is consistent with standard electrical engineering calculations.

Using the correct choice reflects the understanding that increasing the length of the conductor will indeed result in higher resistance, and the value needs to align with SI units to maintain consistency in calculations. This makes option B the accurate representation of how resistance is calculated for a conductor when keeping track of unit conversions.