I have some questions regarding the formula R = p * l/a Where R is resistance, p is resistivity, l is length and a is cross-sectional area = pi*r^2 What units should l and a should be in? When I try to look up problems, I see a lot of conversion to cm. Wouldn't it be m? Here's my problem R = ? p = 3.5e-4 diameter = 2.4mm length = 18 cm What should length and radius be converted to get Ohms?