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

A metal cube of side 5 cm is charged with $6 \mu \mathrm{C}$. The surface charge density on the cube is
  1. $0.125 \times 10^{-3} \mathrm{C} \mathrm{m}^{-2}$
  2. $0.25 \times 10^{-3} \mathrm{C} \mathrm{m}^{-2}$
  3. $4 \times 10^{-3} \mathrm{C} \mathrm{m}^{-2}$
  4. $0.4 \times 10^{-3} \mathrm{C} \mathrm{m}^{-2}$

Solution

$\Rightarrow$ In metal all the charge is present on surface. $Q=6 \mu C$ Total surface area $S=6 a^2$ $=6 \times\left(5 \times 10^{-2}\right)^2$ $=6 \times 25 \times 10^{-4}$ $=150 \times 10^{-4} \mathrm{~m}^2$ Surface charge density $\sigma=\frac{Q}{S}$ $=\frac{6 \times 10^{-6}}{150 \times 10^{-4}}$ $=0.4 \times 10^{-3} \mathrm{C} \mathrm{m}^{-2}$ .

Asked in: NEET 2024 (Re-NEET)

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