**Core Concept**
Ohm's law describes the fundamental relationship between the current flowing through a conductor, the electromotive force (voltage) driving the current, and the resistance encountered by the current. This principle is crucial in understanding how electrical circuits function and is commonly applied in medical devices, diagnostic equipment, and therapeutic modalities.

**Why the Correct Answer is Right**
Ohm's law states that the current (I) flowing through a conductor is directly proportional to the electromotive force (E) applied and inversely proportional to the resistance (R) encountered. Mathematically, this is expressed as I = E/R. In a circuit, the electromotive force is the driving force that pushes electrons through the conductor, while resistance opposes the flow of electrons. The correct answer represents the correct mathematical relationship between these three variables.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it incorrectly states the relationship between current, electromotive force, and resistance. The correct relationship is I = E/R, not I = E x R.

**Option B:** This option is incorrect because it incorrectly states the relationship between current, electromotive force, and resistance. The correct relationship is I = E/R, not I = R/E.

**Option C:** This option is incorrect because it incorrectly states the relationship between current, electromotive force, and resistance. The correct relationship is I = E/R, not I = E - R.

**Clinical Pearl / High-Yield Fact**
When applying Ohm's law in medical settings, it's essential to remember that resistance can vary depending on the type of conductor, temperature, and other factors. This can impact the performance of medical devices and diagnostic equipment.

**Correct Answer: C. I = E/R**