At what distance from a 10 nC charge is the field strength 300 V / m?

The field strength E is calculated by the formula:

E = k. q / r ^ 2;

E = 300 V / m;

here the proportionality coefficient k = 9.109:

this is a constant value and depends on the frame of reference we have chosen. In this task, we use SI – the international system

q value of electric charge 10 nC = 10. 10-9 Cl;

from the basic formula of tension, we derive the value of the square of the distance:

r ^ 2 = k. q / E;

r ^ 2 = 9. 10 ^ 9. ten . 10 ^ -9 / 300 = 3/10 = 0.3 (m2);

now we extract the root from 0.30 = 0.54 (m) or 54 cm.

the answer is at a distance of 54 cm from the point charge.