h, (3)P4=P6 4=PA+p水gh2+p水gX P6=PCp水gX十p汞gh2 PC=PAp汞gh2+P水gh2 =76610Pa(绝压) PC=24720Pa(真空度)（3）P4 = P6 P4 = PA+ρ水gh2+ ρ水gx P6 = PC+ ρ水gx +ρ汞gh2 PC = PA-ρ汞gh2+ ρ水g h2 = 76610 Pa（绝压） PC = 24720 Pa （真空度） h2 A B C 1 2 3 4 5 6 h2