A charged nonconducting rod, with a length $L$ and a cross-sectional
area $A$, lies along the positive side of an $x$ axis with one end at the
origin. The volume charge density $\rho$ is charge per unit volume.
NOTE: Express your answer in terms of the given variables using $e$ to represent the
elementary charge.
(a) How many excess electrons are on the rod if $\rho$ is uniform?
$n_a = $
(b) How many excess electrons are on the rod if $\rho$ is nonuniform, with
a value given by $\rho = bx^2$, where $b$ is a constant with the
appropriate units?
$n_b = $
