Question

The electric field in a region is radially outward and at a point is given by $E=250\, r\, V / m$ (where $r$ is the distance of the point from origin). Calculate the charge contained in a sphere of radius $20\, cm$ centred at the origin

• A. $2.22 \times 10^{-6} \,C$
• B. $2.22 \times 10^{-8} \,C$
• C. $2.22 \times 10^{-10} \,C$
• D. Zero

Answer 1

Answer: (C)

$E=\frac{1}{4 \pi \varepsilon_{0}} \cdot \frac{Q}{r^{2}} $
$250\, r=\frac{9 \times 10^{9} \cdot Q}{r^{2}}$
Use $r=20 \times 10^{-2} \,m$
Find $Q=?$
$Q=2.22 \times 10^{-10} \,C$