Formula Electric current (definition) Electric charge Time
$$I ~=~ \frac{Q}{t}$$ $$I ~=~ \frac{Q}{t}$$ $$Q ~=~ I \, t$$ $$t ~=~ \frac{Q}{I}$$
Electric current
\( I \) Unit \( \text{A} \) Electric current is the amount of charge \(Q\) that crosses the cross-sectional area of a wire within a time period \(t\). Electric current is therefore charge per time.
Electric charge
\( Q \) Unit \( \text{C} \) This is the amount of charge that has passed through the cross-sectional area of a wire within the time \(t\).
If the individual (positively) charged particles carry the charge \(q\) and \(N\) particles have passed through the cross-sectional area in the time \(t\), then the charge passed through:\[ Q ~=~ N \, q \]
Time
\( t \) Unit \( \text{s} \) Time period during which the charges were counted through a cross-sectional area.