Electricity for public schools and colleges . lvanometer without whichsignals by cable would hardly have been possible. In h\?, mirror galvanometer we may notice the following mainpoints of interest. (i.) As the instrument is usually intended to be used in circuitswhere the resistance is already very great, there are often manythousand turns of (necessarily) fine wire ; this multiplies thestrength of the field due to the current without perceptiblydiminishing this latter. For the total resistance will not relativelybe much increased. (ii) The needle is a very small bit of magnetised watch-spri
Electricity for public schools and colleges . lvanometer without whichsignals by cable would hardly have been possible. In h\?, mirror galvanometer we may notice the following mainpoints of interest. (i.) As the instrument is usually intended to be used in circuitswhere the resistance is already very great, there are often manythousand turns of (necessarily) fine wire ; this multiplies thestrength of the field due to the current without perceptiblydiminishing this latter. For the total resistance will not relativelybe much increased. (ii) The needle is a very small bit of magnetised watch-spring. Having little i?iass and inertia, its movements follow anyfluctuations in the current almost instantaneously. (iii.) A controlling magnet enables one to vary the sensitive-ness of the instrument at will, as explained in § 9. (iv.) The same controlling magnet enables one, if need be, tobring the needle to rest in any position ; and. aided by the methodof suspension mentioned below, to work the instrument even on 284 ELECTRICITY CH.
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Keywords: ., bookcentury1800, bookdecade1890, bookpubl, booksubjectelectricity
