  Various effects of the noise intensity upon the solution $u(t,x)$ of the
stochastic heat equation with Dirichlet boundary conditions on $[0,1]$ are
investigated. We show that for small noise intensity, the $p$-th moment of
$\sup_{x \in [0,1]} |u(t,x)|$ is exponentially stable, however, for large one,
it grows at least exponentially. We also prove that the noise excitation of the
$p$-th energy of $u(t,x)$ is $4$, as the noise intensity goes to infinity. We
formulate a common method to investigate the lower bounds of the above two
different behaviors for large noise intensity, which are hard parts in
\cite{FoJo-14}, \cite{FoNu} and \cite{KhKi-15}.
