Short Answer 
Electrical resistance measures how much a material hinders electric current, influenced by atomic structure and free electrons. Copper has lower resistance than aluminum due to more free electrons, making it a better conductor, and resistance can be calculated with the formula R = ρL/A, depending on material properties and dimensions.
Step 1: Understand Electrical Resistance
Electrical resistance is a measure of how much a material opposes the flow of electric current. Different materials exhibit different levels of resistance, primarily due to their atomic structure and the availability of free electrons. The more free electrons a material has, the lower its resistance will be, making it a better conductor of electricity.
Step 2: Compare Copper and Aluminum
Copper and aluminum are two commonly used conductive materials, but they have distinct differences in their resistance properties. Copper has a higher number of free electrons compared to aluminum, resulting in lower resistance. This means that copper allows electricity to flow more easily than aluminum, making it a preferred choice in many electrical applications.
Step 3: Factor in Resistance Calculation
The resistance of a material can be calculated using the formula R = ρL/A, where:
- R = resistance
- ρ = resistivity of the material
- L = length of the conductor
- A = cross-sectional area of the conductor
This formula shows that resistance depends on the material’s properties as well as its physical dimensions, allowing comparisons between different conductors based on these factors.