A metal cube of side \(5\mathrm{cm}\) is charged with \(6\mu \mathrm{C}\). The surface charge density on the cube is : […

In metal all the charge is present on surface.

\(\mathrm{Q}=6 \mu C\)

Total surface area \(S=6 a^2\)

\(\begin{aligned}
& =6 \times\left(5 \times 10^{-2}\right)^2 \\
& =6 \times 25 \times 10^{-4} \\
& =150 \times 10^{-4} \mathrm{~m}^2
\end{aligned}\)

Surface charge density \(\sigma=\frac{Q}{S}\)

\(\begin{aligned}
& =\frac{6 \times 10^{-6}}{150 \times 10^{-4}} \\
& =0.4 \times 10^{-3} \mathrm{Cm}^{-2}
\end{aligned}\)