Using I = Q/t — charge, current and time

5 minAS Level9.1.3

By the end of this lesson

By the end you can confidently use $I = Q/t$ to find any one of current, charge or time, with unit conversions (mA, μA, minutes, hours, etc.).

The formula triangle

The relationship $I = Q/t$ is simple but appears constantly in exams. Think of it as a triangle:

     Q
   /   \
  I  ×  t

Always work in SI base units: amperes (A), coulombs (C), seconds (s).

Worked example: Basic charge calculation

A current of 0.50 A flows for 2.0 minutes. What charge passes?

Have a go first?

Worked example: Finding time

A charger delivers a constant current of 2.0 A. How long (in hours) to deliver 3600 C of charge?

Have a go first?

Quick check

CalculateQuestion 1 · Recall

CalculateQuestion 2 · Recall

CalculateQuestion 3 · Recall

Answer the 3 questions above to continue.