Final answer:
The resistance of a protective floor mat at a workstation should be high enough to keep any potential current through a person below harmful levels. Typically, for a source of 120 V AC, a safe threshold of 1 mA would require a minimum resistance of 120,000 ohms, or 120 kΩ.
Step-by-step explanation:
For proper personnel protection at a workstation, a floor mat should have enough resistance to significantly reduce the potential current that might pass through a person if they come into contact with an electrical source. To calculate the minimum resistance of the path the current follows through the person, the acceptable current that is safe yet unfelt must be considered. Based on typical safety standards, this current is often around 1 milliampere (mA), which is below the level that a person can feel.
Considering the body's resistance can vary a great deal, from around 1,000 ohms when wet to 100,000 ohms or more when dry, the resistance of the protective mat should be high enough to keep the current below harmful levels. For example, if the source is 120 V AC, and the safe threshold is 1 mA, we use Ohm's Law (V = IR) to calculate the minimum resistance required for safety, which would be 120,000 ohms (or 120 kΩ). This is a very simplistic example, and actual safety measures will consider various conditions, including body resistance, environment, and grounding methods.