The field strength at a distance of 30 cm from a point electric charge is 900 V / m.

The field strength at a distance of 30 cm from a point electric charge is 900 V / m. What is the field strength at a distance of 10 cm from the charge?

Initial data: E1 (field strength at a distance r1 from a point charge) = 900 V; r1 (first distance from a point charge) = 30 cm (0.3 m); r2 (second distance from the point charge) = 10 cm.

Since the magnitude of the charge is constant, the equality will be true (E = k * q / r ^ 2): q = E1 * r1 ^ 2 / k = E2 * r2 ^ 2 / k, whence E2 = E1 * r1 ^ 2 / r22 …

Let’s make the calculation: E2 = 900 * 0.3 ^ 2 / 0.1 ^ 2 = 8100 V / m (8.1 kV / m).

Answer: The field strength at a distance of 10 cm from the charge is 8.1 kV / m.