Q. Two insulated charged conducting spheres of radii 20 cm and 15 cm respecting and having an equal charge of 10 $\mu$C are connected by a copper wire and then they are separated. Then
A) Both spheres will have equal charges
B) Surface charge density on the 20 cm sphere will be greater than that on the 15 cm sphere
C) Surface charge density on the 15 cm sphere will be greater than that on the 20 cm sphere
D) Surface charge density on the two sphere will be equal
Explanation
(c) On connecting, potential becomes equal$\ \ q \propto C \propto r$ and $\sigma = \frac{q}{A} \propto \frac{r}{r^{2}} \rightarrow \frac{1}{r}$
$\therefore\ $Surface charge density on 15 cm sphere will be greater than that on 20 cm sphere.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.