Atungsten wire is 1.50 m long and has a diameter of 1.00 mm. at 20°c a current of 50 ma flows through this wire. the temperature coefficient of resistivity for this tungsten is 4.5 × 10-3/c°, and its resistivity at 20°c is 5.6 × 10-8 ω ∙ m. (a) what is the potential difference across the ends of this wire at 20°c? (b) if the wire temperature increases by 100°c, what potential difference across its ends is now required to produce a current of 50 ma?