ARRL Technician Practice Exam 2026 – 400 Free Practice Questions to Pass the Exam

The correct formula to calculate resistance in a circuit is given by the relationship defined by Ohm's Law, which states that resistance (R) is equal to the voltage (E) across the circuit divided by the current (I) flowing through it. This is mathematically expressed as R = E / I.

In practical terms, this means that if you know the voltage applied across a circuit and the current that is flowing through it, you can easily calculate the total resistance in that circuit. This formula is essential for understanding how electrical components operate together in any circuit and is a foundational concept in electronics.

The other choices do not accurately represent the relationship between voltage, current, and resistance according to Ohm's Law. Some represent the relationships of current and voltage in ways that do not conform to the established principles of electrical theory, making them inappropriate for determining resistance directly.