Electrical Inspection, Testing and Certification Practice Exam

When the cross-sectional area (CSA) of a conductor increases, what happens to its resistance?

1. It increases

2. It decreases

3. It remains the same

4. It fluctuates

The correct answer is: It decreases

When the cross-sectional area (CSA) of a conductor increases, its resistance decreases. This relationship is based on the principle that resistance is inversely proportional to the cross-sectional area of the conductor, as described by the formula for resistance: \[ R = \frac{\rho L}{A} \] where \( R \) is resistance, \( \rho \) is the resistivity of the material, \( L \) is the length of the conductor, and \( A \) is the cross-sectional area. As the CSA (A) increases, the denominator in the equation becomes larger, which results in a lower overall resistance (R) for the conductor. It's important to understand the practical implication of this principle. In electrical systems, conductors with larger cross-sectional areas can carry more current with less resistance, leading to lower energy losses in the form of heat. This is why, in applications requiring high current, thicker wires are used to decrease resistance and enhance performance.