A 100-cm-long copper wire of radius 0.50 cm has a potential difference across it sufficient to produce

Question:

A 100-cm-long copper wire of radius 0.50 cm has a potential difference across it sufficient to produce a current of 3.0 A at 20°C.
(a) What is the potential difference?
(b) If the temperature of the wire is increased to 200°C, what potential difference is now required to produce a current of 3.0 A?