Which variable in the equation for electrical resistance is represented by 'p'?

• A. Potential difference
• B. Resistivity
• C. Current
• D. Length

Answer: (B)

In the context of electrical resistance, the variable 'p' represents resistivity. This is a fundamental property of materials that quantifies how strongly a given material opposes the flow of electric current. Resistivity is a critical factor because it can vary significantly from one material to another. For instance, metals like copper have low resistivity, allowing for easy flow of electric current, whereas rubber has high resistivity, making it a good insulator.

The resistance of a cylindrical conductor, such as a wire, can be expressed using the formula R = (p * L) / A, where 'R' is resistance, 'p' is resistivity, 'L' is the length of the conductor, and 'A' is the cross-sectional area. This demonstrates how resistivity is not just a defining property of a material but also plays a crucial role in determining how resistance behaves in practical applications.

Understanding resistivity is essential for materials science and electrical engineering, as it informs choices about which materials to use in different electrical applications based on how much resistance they will introduce into a circuit.