(a) The amount of charge passed in time `t` through a cross-section of wire is
`q = alpha t - beta t^2`
where `alpha` and `beta` are constant.
(i) Find current in terms of time `t`.
(ii) Sketch `i` versus `t` graph.
(b) The current through a wire depends on time as
`i = 4 + 3t + 2t^2`
Find the charge crossed through a section of wire in `6 sec`.