Which factor is NOT a major determinant of skin resistance?

• A. Contact area
• B. Skin moisture
• C. Source voltage
• D. Bone density

Answer: (D)

Skin resistance is set by how easily current can pass through the skin itself, which depends mainly on the conductive path you’re creating. When you increase the contact area, you spread the current over a larger surface, which lowers resistance. If the skin is moist, ions conduct electricity better, also lowering resistance. The applied voltage doesn’t determine the skin’s intrinsic resistance; it’s the force that pushes current through the path defined by the skin and its condition (Ohm’s law: current depends on voltage and resistance). Bone density isn’t part of the surface impedance and doesn’t change how the skin resists current, so it isn’t a major determinant.