真空组件

       本展品利用真空泵、电磁阀和一套真空管路系统分别组成六个真空室，完成：“没有空气能听见声音吗？“希洛发动机”；“空气的重量”；“热风轮需要空气”；“瘪了的气球为甚麽又鼓了起来？”；“甚麽力量使水自行流动”等六项真空实验：“没有空气能听见声音吗？”按下按钮后，玻璃罩内的警铃发出警报声，持续一段时间之后，自动将玻璃罩与真空系统接通，使罩内空气越来越稀薄，警铃声也逐渐减弱。若干秒后，玻璃罩内又重新充入空气时，警报声逐渐恢复。其原理是：罩内空气被抽空后，罩内没有空气作为媒质，声音无法传播，因而，警铃声听不见了。“希洛发动机” 玻璃罩内的中空球，两端靠顶尖垂直支撑在支架上，球的水平面直径两侧有一对反向对置的喷嘴。当罩内的空气被抽出时，球绕垂直轴转动。为什么玻璃罩接通真空系统时，球会转起来？又为什么会停止？原来玻璃罩接通真空系统后，球内的空气亦从喷嘴中抽出，从球内抽出的空气对球的反作用力，恰好形成一对力偶，使球绕垂直轴转动，直到中空球内的空气被抽空后，不再有空气从喷嘴中喷出，转动亦即停止。“空气的重量”玻璃罩内天平两侧各放一个玻璃球，两球直径相同，一球有孔，另一个无孔。天平是平衡的。当罩内的空气被抽空时，天平倾斜了。因为玻璃罩接通真空系统后，有孔玻璃球中的空气被抽出，无孔的球内空气仍存在，从而天平不再平衡了。“风轮需要空气”一射灯放在导流筒内，导流筒下端有通气孔，上升的热气流带动风轮旋转。玻璃罩内的空气被抽空时，热风轮就不转了。因为玻璃罩接通真空系统后，玻璃罩内的空气被抽空时，没有空气流动，没有热气流上升，自然不能带动风轮转动。“瘪了的气球为什么又鼓了起来？”玻璃罩内有一瘪了的气球，按下按钮，你会发现瘪了的气球又鼓了起来。这是因为瘪了的气球内部仍残留有部分空气，当玻璃罩内的空气被抽空时,外部气压低，球内的气压高于球外部气压，因而球内气体膨胀，气球又鼓了起来。“甚麽力量使水自行流动”玻璃罩内，放置两个玻璃筒，两者之间用倒置的U形管相连，左面的玻璃筒上有个小口，是用橡皮塞子封住的；右面筒上也有一小口，是敞开的；两边玻璃筒内有等高的液面。按下按钮，当玻璃罩被抽空时，左筒中的液体沿倒置的U形管流入右筒，当玻璃罩与大气相通（真空表回零）时，则右面玻璃筒中的液体， 又流回到左面。是 “ 什么力量使水自行流动 ”？当玻璃罩被抽空时，由于左、右两筒的压力差，左筒中的液体沿倒置的U形管流入右筒，右筒液面高于左筒，当玻璃罩与大气相通（真空表回零）时，则右面玻璃筒中的液体， 又与大气相通，在大气压的作用下流回到左面。    

Vacuum Experience

        There are six tests here to demonstrate the physical characteristics and the application of the vacuum. Press the button to exhaust the air to see what is happening in these six tests.“Sound Without Air?”This experience shows you that the transmission of sound needs air as media.When the button is pressed down, the siren begins to work. After a few second, the air inside the glass jar is totally removed, so there is no media for the transmission of the alert sound, the sound can no longer be heard. 
        After another a few second, the air newly entered the glass jar enables the sound transmission again, so the alert sound can be heard again.“Hero’s Jet Engine”This is a very simple jet engine enabled by vacuum.There are two spouts at opposite side of the ball. When the air inside the glass jar is removed, the air inside the ball jet out through the two spouts. The two jets with opposite direction make the ball rotate, like rotor in a engine. When there is no more air in the ball, the jet engine stops.“The Weight Of Air” There are two glass balls in this system, each at a side of the balance, one with a hole and the other without.When the air in the glass jar is removed, the two balls are in different situation: the ball with hole has no air inside however the other one has. The weight of the air in the ball without hole makes the balance unbalanced.This experience shows although air can not be seen, it can be weighted.“Windmills Need Air”When the glass jar is opened to the atmosphere, the air inside the glass jar is warmed by the lamp. The up air current makes the windmill to rotate. When the air is removed from the jar , there is no more air current, so the windmill stops.“Blowing up "Balloon From The OutSide Because there is still air in the shrunken balloon, when the air pressure outside the balloon decreased, the air pressure inside the balloon makes the balloon distended.The Force Behind Water Flowing This experience tells you how air pressure can be used There are two glass bottles in the glass jar, connected with a U tube. The top of the left bottle is sealed by rubber stopper and the top of the right bottle is open. There is liquid with equal height in the two bottles. When the air in the glass jar  is exhausting, the pressure over the liquid of the right bottle is decreasing, but the pressure over the liquid of the left bottle remains constant, so the liquid flows gradually from the left bottle to the right bottle through the U-tube. When the air in the right returns to the normal air pressure, the liquid flows back.It is the air pressure make the flow of the liquid.