1. The problem statement, all variables and given/known data You have a 25 mm long cylindrical carbon resistor, with a cross-section of radius 15·10-6 m. What is its resistance? 2. Relevant equations Resistance = pL/A where p is the resistivity of the material, L is the length, and A is the area(?). Also, given is that the p for a carbon material is 3500 x 10^-8 ohm meters. And 25 mm = .025 m. 3. The attempt at a solution I'm stuck on this problem because I can't figure out what the A in the equation works out to be or refers to. I know it's an area, but what area? The area of a cylinder? The surface area? I'm not quite sure. I assumed A referred to the surface area of the cylinder, and given the length and cross sectional radius, I computed the surface area. But when I plugged in the formula (3500 x 10^-8) (.025 m)/ surface area of cylinder, the resistance value I got was incorrect. I know this is a really nit picky question, but I'm going insane trying to figure out what the area refers to in this particular problem. Any help would be appreciated.