A Circumcircle of Maximal Area

The ellipse $C:\dfrac{x^2}9+\dfrac{y^2}3=1$ has left vertex $A$. A line $l$ through the point $B(1,0)$ meets $C$ at two points $P$ and $Q$. Let $N$ be the circumscribed circle of $\triangle APQ$.

1. When $l$ is perpendicular to the $x$-axis, find the equation of the circle $N$. 2. Find the maximum area of the circle $N$.