Charge–current relation: If the current is 2.5 A, how much electric charge (in coulombs) passes a point in 0.2 s?

Introduction / Context:
Current is the time rate of flow of electric charge. Converting between current, charge, and time helps in analyzing pulse currents, capacitor charging, and cumulative energy delivery in circuits.

Given Data / Assumptions:

• Current I = 2.5 A.
• Time interval t = 0.2 s.
• We seek total charge Q crossing a point.

Concept / Approach:
The fundamental relation is Q = I * t, with Q in coulombs, I in amperes, and t in seconds. One ampere equals one coulomb per second.

Step-by-Step Solution:

Verification / Alternative check:
Dimensional check: A * s = C. A back-of-envelope estimate: 2.5 ≈ 2.5, 0.2 ≈ 1/5 → 2.5/5 = 0.5, consistent with the exact arithmetic.

Why Other Options Are Wrong:

• 12.5 C and 5 C: These correspond to multiplying by the wrong time factor (e.g., using seconds as 5 s or 2 s).
• 1.25 C: Would require t = 0.5 s at 2.5 A; not our case.

Common Pitfalls:

• Mistaking milliseconds or minutes for seconds—always convert time units to seconds before applying Q = I * t.

Final Answer:
0.5 C