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2. Electric Potential and Capacitance
medium
The electric potential at a point $(x,\;y)$ in the $x - y$ plane is given by $V = - kxy$. The field intensity at a distance $r$ from the origin varies as
A
${r^2}$
B
$r$
C
$\frac{1}{r}$
D
$\frac{1}{{{r^2}}}$
Solution

(b) ${E_x} = – \frac{{dV}}{{dx}} = – \,ky$; ${E_y} = – \frac{{dV}}{{dy}} = \, – kx$
$E = \sqrt {E_x^2 + E_y^2} = k\sqrt {{x^2} + {y^2}} = kr$=
$E \propto r$
Standard 12
Physics