. A text book of physics, for the use of students of science and engineering . be at right angles to every equi-potential surface. If this were not the case there would be acomponciil of the field parallel to the surface. It follows that linesof force always meet conducting surfaces at right angles, as may bjseen on examining Fig. 863. Charging a conductor by influence.—In the earlier experimentswith Ili< electroscope (p. 923) this was charged by touching it withthe nibbed ebonite rod. There is a better way than this. Let apositively charged body Q (Fig. 861) be brought near to a conductorA
. A text book of physics, for the use of students of science and engineering . be at right angles to every equi-potential surface. If this were not the case there would be acomponciil of the field parallel to the surface. It follows that linesof force always meet conducting surfaces at right angles, as may bjseen on examining Fig. 863. Charging a conductor by influence.—In the earlier experimentswith Ili< electroscope (p. 923) this was charged by touching it withthe nibbed ebonite rod. There is a better way than this. Let apositively charged body Q (Fig. 861) be brought near to a conductorAB supported upon a glass cod in order to insulate it. The presence ofQ, raises the potential everywhere in its neighbourhood ; hence if ABwere originally al the potential of earth it will now have a positivepotential. Bui the nearer parts A will be at a higher potential thanthe more distanl parts B(V=Q//). Hence a current will flow fromA to B. which means thai the cud B will acquire an excess of positivecharge and a of negative charge. This flow will go on until all parts. 3 4 5 6. I « ? PScale of Centimetres Fig. 863.—Equipotential surfaces and lines offorce. :xn CHARGING BY INFLUENCE 933 f + + +B + + + 5 © Q Z^ FIG. 864.—Effect of a charged bodynear a conductor. AB are brought to the same potential, since when the charges are rest, the surface of a conductor must be an equipotential surface. bt the conductor be now connected to earth. A current will >w to earth, since the conductor at a higher potential than earth, ving to the presence of Q,. The >w will continue until AB is reducedthe potential of earth (zero) and I will then retain just sufficientative charge everywhere to pro-ice a negative potential equal to e positive potential Q, so that the tual potential, being the sum of ese, is zero. The distribution of arge will be somewhat as indicated Fig. 865 (a). Now let the earth connection be oken, and then let Q, be removed. le negative charge on AB cannot t aw
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
