I is approximately constant for many conductors at constant temperature. Ohm's law breaks down under extreme conditions for all conductors. Many modern materials do not obey Ohms law under any circumstances. The resistivity and therefore the resistance of most materials depends on the temperature. A copper wire has a length of 160 m and a diameter of 1.00 mm.
V is the battery voltage, so if R can be determined, the current can be calculated.
An aluminum wire has a resistance of 0.10 W . After passing the wire through the die, its length has changed to L' and its cross-sectional area is equal A'. Its final volume is therefore equal to A'L'. A high voltage transmission line has an aluminum cable of diameter 3.0cm, 200km long. This is the power supplied by the emf.