Electric field strength can be described as the ratio of force to charge, i.e., F divided by q. Which option correctly expresses this definition?

• A. F divided by the charge
• B. Voltage
• C. F divided by the test charge
• D. Energy per unit charge

Answer: (C)

Electric field strength is defined as the force that would be exerted on a small test charge per unit of that charge. In other words, E = F/q, where q is the charge of the test particle. Using a test charge ensures we’re measuring how the field acts without disturbing it, and the ratio is specifically the force divided by the test charge. The other terms describe different quantities: voltage is a potential difference, and energy per unit charge is potential energy per unit charge (electric potential). So the precise expression for field strength is the force on a test charge divided by that test charge.