The electric field strength (often just called the electric field) is a fundamental concept in electromagnetism and is defined as the force per unit charge exerted on a test charge placed in the field. To find its derived unit, we need to express it in terms of the basic units of measurement.
The electric field strength \( E \) is given by the formula:
\[ E = \frac{F}{q} \]
where \( F \) is the force experienced by the test charge and \( q \) is the magnitude of the test charge.
In the International System of Units (SI):
- Force \( F \) is measured in newtons (N).
- Charge \( q \) is measured in coulombs (C).
So, the unit of electric field strength can be derived from the unit of force divided by the unit of charge:
\[ \text{Unit of } E = \frac{\text{Unit of } F}{\text{Unit of } q} = \frac{\text{N}}{\text{C}} \]
Thus, the derived unit of electric field strength is newtons per coulomb (N/C).
This unit signifies that an electric field exerts a force of one newton on a charge of one coulomb.