Q. Two metallic charged spheres whose radii are $20cm$ and $10\ cm$ respectively, have each $150\ micro - coulomb$ positive charge. The common potential after they are connected by a conducting wire is
A) $9 \times 10^{6}\ volts$
B) $4.5 \times 10^{6}\ volts$
C) $1.8 \times 10^{7}\ volts$
D) $13.5 \times 10^{6}\ volts$
Explanation
(a) Common potential $V = \frac{Total\ charge}{Total\ capacitance}$
$V = \frac{150 \times 10^{- 6} \times 2}{4\pi\varepsilon_{0}(10 \times 10^{- 2} + 20 \times 10^{- 2})} = 9 \times 10^{6}\ V$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.