A resistor is constructed of a carbon rod that has a uniform cross-sectional area of 5.00 mm2.

Question:

A resistor is constructed of a carbon rod that has a uniform cross-sectional area of 5.00 mm2. When a potential difference of 15.0 V is applied across the ends of the rod, the rod carries a current of 4.00 x 10-3 A. Find
(a) The resistance of the rod and
(b) The rod’s length.