How is electric field strength measured?

The strength of an electric field (E) at any given point is defined as the Coulomb force (F) exerted per unit of positive test charge (q) placed at that location. This relationship is expressed by the formula:

$$E=\frac{F}{q}$$

Because the electric field is a vector quantity, it possesses both magnitude and direction. The magnitude represents the force per unit charge, while the direction is defined as the direction of the force that would be exerted on a positive test charge.12

In the SI system, electric field strength is measured in newtons per coulomb (N/C), which is equivalent to volts per metre (V/m). In the centimetre-gram-second system, it is expressed in dynes per electrostatic unit (esu) or statvolts per centimetre. When multiple charges are present, the total electric field at a specific point is determined by calculating the vector sum of the individual fields produced by each source charge.12