A Physical Treatise on Electricity and Magnetism

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D. Appleton, 1880 - Electricity - 618 pages
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Page 19 - The repulsion between two small bodies charged respectively with e and e' units of electricity is numerically equal to the product of the charges divided by the square of the distance. Dimensions of the Electrostatic Unit of Quantity. 42.] If [Q] is the concrete electrostatic unit of quantity itself, and e, e...
Page 25 - A galvanometer whose needle comes quickly to rest instead of repeatedly swinging to and fro, through being heavily damped. Dielectric. Any material which offers high resistance to the passage of an electric current. Difference of Potential. When electricity moves, or tends to move, from one point to another, there is said to be a difference of potential between them.
Page 213 - ... boiling-point : the salt, which is a nearly insoluble white powder, should be well washed in distilled water, and care should be taken to obtain it free from the mercuric sulphate (persulphate), the presence of which may he known by the mixture turning yellowish on the addition of water.
Page 293 - X. fig. 1, has been found very convenient, as it can be immersed in water during an observation. The wire is twice coated with silk, and protected by being imbedded in solid paraffin. Besides the coils already mentioned, ten unit-coils have been made, which will be deposited at the Kew Observatory. Any one possessing a copy of the BA unit may have it compared at any future time against one of these coils for a small payment. Of the coils to be sent to Kew, two are of the platinum-silver alloy, two...
Page 157 - Having made many and diverse compasses, and using alwaies to finish and end them before I touched the needle, I found continuallie that after I had touched the yrons with the stone, that presentlie the North point thereof woulde bend or decline downwards under the horizon in some quantitie; insomuch that to the flie of the compass, which was before levell, I was still constrained to put some small piece of ware on the South point and make it equall againe.
Page 212 - The battery is formed by employing pure mercury as the negative element, the mercury being covered by a paste made by boiling mercurous sulphate in a thoroughly saturated solution of zinc sulphate, the positive element consisting of pure distilled zinc resting on the paste.
Page 190 - Thus we see that the changes in the magnetic elements depend principally on the relative positions of the sun and moon with respect to the earth.
Page 1 - ... electricity. But, although we have, or think we have, tolerably clear ideas of the character of the motion of heat, our ideas are very unclear as to the precise nature of the change which this motion must undergo in order to appear as electricity ; in fact, we know as yet nothing about it." Gordon wrote, " We have as yet no conception of electricity apart from the electrified body ; we have no experience of its independent existence.
Page 207 - ... than that of sulphate of zinc alone, so that it cannot get to the zinc except by diffusion. To retard this process of diffusion, a siphon, consisting of a glass tube stuffed with cotton wick, is placed with one extremity midway between the zinc and copper. and the other in a vessel outside the cell, so that the liquid is very slo-wly drawn off near the middle of its depth. To supply its place, water, or a weak solution of sulphate of ainc, is added above when required.
Page 72 - ... 145. If it is then heated to a degree rather greater than that of boiling water, it froths very much, and seems to lose a good deal of watery matter, and if it is kept at this heat till it has ceased frothing, it will then bear being heated to a much higher degree without frothing or boiling. Bees wax thus prepared I call dephlegmated. In order that the plates of dephlegmated bees- wax should all be equally so, I dephlegmated some bees wax with a pretty considerable heat, and suffered it to...

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