Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . be supposed that,as the electricity1^ which flows fromC to A in theupper part of thewire must pass ina contrary direc-tion, in returningfrom A to B, be-low (the cup Cbeing connectedwith the positivepole of the bat-tery, and B with the negative), the influence of theone part of the wire would neutralize that of theother; for it has already been stated that the needleis deflected to one side or the other, according to thedirection of the electrical curr
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . be supposed that,as the electricity1^ which flows fromC to A in theupper part of thewire must pass ina contrary direc-tion, in returningfrom A to B, be-low (the cup Cbeing connectedwith the positivepole of the bat-tery, and B with the negative), the influence of theone part of the wire would neutralize that of theother; for it has already been stated that the needleis deflected to one side or the other, according to thedirection of the electrical current. And this wouldin fact be the case, if the returning part of the wirewere upon the same side of the needle with the otherpart, and at an equal distance from it. But a wiretransmitting an electrical current, when passing belowthe needle, will produce an effect the reverse of thatproduced by one passing above, if tlie current in bothcases flows in the same direction. Hence, if thedirection of the electric current is reversed in thewire which passes below, it will exert a force aux-iliary, and not antagonist, to that of the wire passing. 100 DAVISS MANUAL. above. This is the case with the arrangement hererepresented. The two portions of the wire are notallowed to touch each other where they cross, butare insulated at that point by some non-conductor ofelectricity, as by being wound with thread. Instru-ments of a variety of forms are constructed on theabove principle, and are called galvanoscopes or gaUvanometejs, as they serve to indicate the presence of acurrent of electricity, and in some degree to measureits quantity. 159. The vertical portions of the wire also aidin deflecting the needle ; as may be shown by con-necting both the cups B and C with one pole of thebattery by two wires of equal length and thickness,and the cup A with the other pole (say the positive).The current will then be divided into two portionsvery nearly equal, both flowing in the same direction,and at
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
