JEE Adv. 2013: $K\left[ {\frac{x}{{{{({x^2} + {y^2})}^{3/2}}}}\hat i + \frac{y}{{{{({x^2} + {y^2})}^{3/2}}}}\hat j} \right]$

Solution

The equation of the circle is x²+y²=a²

Hence, (D)