Bài 5: Người ta truyền tải đi một công suất điện có giá trị là 10 MW, bằng đường dây dẫn có điện trở 4 , và đặt vào hai đầu đường dây một hiệu điện thế xoay chiều là 20 kV. Tính: a/. Công suất hao phí do tỏa nhiệt trên đường dây. b/. Để công suất hao phí do tỏa nhiệt trên đường dây giảm đi 25 lần, hiệu điện thế ở hai đầu đường dây dẫn phải có giá trị mới là bao nhiêu?

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