Question

A point charge produces an  electric field of magnitude 5.0 NC⁻¹ at a distance of 40 cm from it. What is the magnitude of the charge?

Answer 1

Given:
Magnitude of the electric field, E = 5.0 NC⁻¹ at a distance, r = 40 cm = 0.4 m 
Let the magnitude of the charge be q .  

\[E = \frac{1}{4\pi \epsilon_0}\frac{q}{r^2}\] 

\[ \Rightarrow 5 . 0 = 9 \times  {10}^9  \times \frac{q}{\left( 0 . 4 \right)^2}\] 

\[ \Rightarrow q = 8 . 9 \times  {10}^{- 11}   C\]