Bài 2. (3,5 điểm) Người ta bỏ một thỏi sắt hình trụ có diện tích đáy 5cm2, khối lượng m1 = 200g có nhiệt độ t1 = 3770C vào một bình hình trụ có diện tích đáy S = 20cm2 chứa m2 = 500g nước ở nhiệt độ t2 = 200C. Bỏ qua mọi hao phí. 1. Tính nhiệt độ của nước khi cân bằng nhiệt được thiết lập. Bỏ qua phần nước đã bị hóa hơi. 2. Do có một lượng nước bị hóa hơi, nên nhiệt độ cân bằng của hệ là t = 280C. a. Tính lượng nước đã bị hóa hơi. b. Tính mực nước chênh lệch trong bình trước và sau khi thả khối trụ, khi cân bằng nhiệt được thiết lập. Cho biết nhiệt dung riêng của sắt là 460 J/kg.K, của nước là 4200 J/kg.K khối lượng riêng của sắt D1 = 7800 kg/m3, khối lượng riêng của nước D2 = 1000 kg/m3, nhiệt hóa hơi của nước là L = 2,3.106 J/Kg.

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