일반물리학 2 — Current and Resistance: Problem 30

30 A copper wire of cross-sectional area \(2.40 \times 10^{-6} \text{ m}^2\) and length \(4.00 \text{ m}\) has a current of \(2.00 \text{ A}\) uniformly distributed across that area. (a) What is the magnitude of the electric field along the wire? (b) How much electrical energy is transferred to thermal energy in \(30 \text{ min}\)?