实验四:水面圆环取一小段棉线两头打结连成个小环,放在碗中水面上,请你试用火柴梗把它拨成圆环,但拨来拨去无法成圆,如果你用火柴梗蘸一滴洗洁剂滴在这线环中间,真灵光,线环马上自动变圆(图4)。这是因为线环内洗洁剂溶液的表面张力比线环外水的表面张力小,线环外水的收缩力比线环内的收缩力大,线环就被均匀地向外拉成圆环。 Experiment 4: The surface of the water ring Take a short piece of cotton thread knotted into a small ring, on the bowl of water, try sticking matchstick it dial into a ring, but dial to dial can not be a circle, if you use Matchstick dipped in a drop of detergent drops in the middle of this line, really Emmanuel, the ring automatically round (Figure 4). This is because the surface tension of the detergent solution in the loop is smaller than the surface tension of the water outside the loop. The shrinking force of the water outside the loop is greater than the shrinkage force in the loop. The loop is uniformly drawn outward ring.