Q: If a cube of side 5 cm has a charge of 6 microcoulombs, then the surface charge density is:
(a) 4 × 102 μC/m2
(b) 4 × 102 C/m2
(c) 4 × 103 μC/m2
(d) 4 × 103 C/m2
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Ans: (a)
Sol: Surface charge density , $\large \sigma = \frac{Charge}{Surface \; area}$
$\large \sigma = \frac{6 \mu C}{6 \times (5 \times 10^{-2})^2}$
= 4 × 102 μC/m2