A Level Physics Practice Exam

Resistance in a conductor is NOT affected by which of the following?

1. Length of the conductor

2. Resistivity of the material

3. Temperature of the material

4. Cross-sectional area of the conductor

The correct answer is: Temperature of the material

Resistance in a conductor is described by the formula \( R = \frac{\rho L}{A} \), where \( R \) is the resistance, \( \rho \) is the resistivity of the material, \( L \) is the length, and \( A \) is the cross-sectional area. It is important to consider how each factor affects resistance. The length of the conductor positively affects resistance; as the length increases, resistance increases. Similarly, the resistivity of the material directly influences resistance, as different materials have different intrinsic resistivities. The cross-sectional area also plays a crucial role; an increase in area decreases resistance because more paths are available for current to flow. Temperature does influence resistance in conductors, generally causing it to increase in metallic conductors due to increased lattice vibrations that create more collisions for charge carriers. Therefore, while temperature can impact resistance, it is not a fundamental property like the length, resistivity, or cross-sectional area, which dictates the basic relationship defined in the resistance formula. Thus, temperature is the factor that does not fundamentally change the resistance of a conductor in an idealized sense as the other factors do.