Decoding the Drift Current Formula Steps: - Recall the standard equation for current in a conductor: I = n e A v, where I is current, e is charge per electron, A is cross-sectional area, v is drift velocity, and n is electron density. - Analyze the units: I (amperes) = n (electrons/m³) × e (coulombs) × A (m²) × v (m/s), confirming n must be electrons per unit volume for dimensional consistency. - Consider the physical meaning: Current arises from electrons crossing area A at velocity v, so n quantifies electrons available per volume to contribute to flow. - Eliminate options by matching: Only "number per unit volume" fits n's role in the formula. Why C is correct: - In the drift velocity formula I = n e A v, n is defined as the number density of conduction electrons per unit volume, as per solid-state physics. Why the others are wrong: - A: Includes "unit time," which relates to flow rate, not static density. - B: Describes total electrons passing per time, akin to I/e, not n. - …