Question

Current through a wire decreases linearly from $4\text{A}$ to zero in $10\text{s}$. Calculate the charge flown through the wire during this interval of time.

• A. $20\text{C}$
• B. $40\text{C}$
• C. $30\text{C}$
• D. $10\text{C}$

Answer 1

The correct option is A $20\text{C}$

Here, current decreases linearly, so we can apply the concept of average.

Charge flown = average current $\times$ time

$=\left[\frac{4+0}{2}\right]\times 10=20\text{C}$

Therefore, $\left(a\right)$ is the right choice.

Why this question ? Here charge flown can be easily calculated from law of averages. Note : If the current was not decreasing linearly we would have rather used the technique of integration.