The charge flowing in a conductor varies with time as Q = at - bt2, then the current:
Answer & explanation
Correct answer: option 4
According to question,
$\mathrm{Q}=\mathrm{at}-\mathrm{bt}^2 \Rightarrow \mathrm{i}=\frac{\mathrm{dQ}}{\mathrm{dt}}=\mathrm{a}-2 \mathrm{bt}$
$\mathrm{i}=0 \text { at } \mathrm{t}=\frac{\mathrm{a}}{2 \mathrm{b}}$
$\frac{\mathrm{di}}{\mathrm{dt}}=-2 \mathrm{b}$