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J. Perelman
"Entertaining physics". Book 2.
Chapter 8. The magnetism. Electricity


It is very easy to have a small fountain of rubber tubing, one end of which is immersed in a bucket, set on a hill, or put on a water faucet. The outlet tube should be very little, so that the fountain was broken in thin streams; the easiest way to achieve this, inserting a free end of a piece of pencil, from which the graphite is removed. For the sake of convenience of handling this fountain strengthen the free end in an inverted funnel, as shown in the figure.

Thundery rain in miniature.

Let this fountain with a height of two feet and sending a stream vertically, zoom in to him rubbed by a cloth stick of sealing wax or hard rubber comb. You will immediately see a rather unexpected thing: separate streams flowing part of the fountain will merge into one continuous stream, which with a noticeable noise hits on the bottom substituted plates. The sound is reminiscent of the characteristic noise of the thundering downpour. "No doubt, " observes on this occasion physicist Boyce - that it is for this reason drops of rain during a thunderstorm differ such magnitude". Remove the wax, and the fountain immediately again sprayed, and the characteristic knock will be replaced by a soft noise atomized jet.

Before the laity you can act a stick of sealing wax, as the magician "magic" wand.

The explanation for this unexpected effect of electric charge on the fountain is based on the fact that the drops electrified through impact, and turned to wax some of the droplets is electrified positively, the opposite - negative; thus, the oppositely electrified some of the droplets are in close proximity and, being drawn, the force drops to merge.

The effects of electricity on water jet you can find and easier; it is sufficient to approximate held on ebony hair comb to thin stream of water flowing from the faucet: jet becomes solid and noticeably bent toward the crest, sharply deviating to the side.

Water jet is deflected by the approximation of electrified crest.

The explanation of this phenomenon is harder than the previous; it is connected with the change of surface tension under the action of electric charge.

Before the laity you can act a stick of sealing wax, as the magician "magic" wand.

Note incidentally that the ease with which electric charge is formed by friction, due to the electrification of the transfer belt rubbing on the pulley. Eye-catching electric spark present in several plants in danger of fire. To avoid this, silver gear straps: thin layer of silver makes the strap conductor of electricity, and the charge accumulation becomes impossible.

Entertaining physics J. Perelman


System Orphus


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