Find the charge q that produces a field strength E = 180,000 N / C at a distance R = 0.5 m in vacuum.

The field strength of a point charge is determined from the expression:
E = kq / r², where q is the charge that creates the field, k is the coefficient 9 * 10 ^ 9, r is the distance to the charge.
Let us express the charge from this expression:
q = E * r² / k
Let’s substitute numerical data into this expression:
q = E * r² / k = 180,000 * 0.5² / (9 * 10 ^ 9) = 5 * 10 ^ -4 Cl.
Answer: charge 5 * 10 ^ -4 Cl.