The magnitude of point charge due to which the electric field 30 cm away has the magnitude ,2 NC-1 will be

Question

The magnitude of point charge due to which the electric field 30 cm away has the magnitude ,2 NC-1 will be (A)  2 × 10-11 C  (B)  3 × 10-11 C  (C)  5 × 10-11 C  (D)  9 × 10-11 C

Tardigrade Admin · Accepted Answer

E = (kq/r2) q = (Er2/k) = (2 ×(0.3)2/9×109) = (2×9 ×10-2 ×10-9/9) ∴ q = 2 ×10-11 C

Q. The magnitude of point charge due to which the electric field 30 cm away has the magnitude , $2 N C^{- 1}$ will be

$2 \times 1 0^{- 11} C$

$3 \times 1 0^{- 11} C$

$5 \times 1 0^{- 11} C$

$9 \times 1 0^{- 11} C$

$E = \frac{k q}{r ^{2}}$
$q = \frac{E r ^{2}}{k} = \frac{2 \times ( 0.3 ) ^{2}}{9 \times 1 0 ^{9}} = \frac{2 \times 9 \times 1 0 ^{- 2} \times 1 0 ^{- 9}}{9}$
$∴ q = 2 \times 1 0^{- 11} C$

Q. The magnitude of point charge due to which the electric field 30 cm away has the magnitude ,2NC−1 will be

2×10−11C

3×10−11C

5×10−11C

9×10−11C