Electricity for public schools and colleges . Fig. i. CH. VI. ELEMENTARY DISCUSSION OF CONDENSERS 95 Comparing with the results obtained in Chapter XXL, wherewe employ electrical currents over whose increase and decrease wehave complete control, it would seem that as the discharge fromB to A begins, there is induced a rush in the contrary directionfrom D to C ; while as the discharge from B to A fades away,there is induced a rush from C to D in the same direction. It would seem also that the direct induced rush from C to Dis the more violent of the two, for the reason that the cessation ofthe
Electricity for public schools and colleges . Fig. i. CH. VI. ELEMENTARY DISCUSSION OF CONDENSERS 95 Comparing with the results obtained in Chapter XXL, wherewe employ electrical currents over whose increase and decrease wehave complete control, it would seem that as the discharge fromB to A begins, there is induced a rush in the contrary directionfrom D to C ; while as the discharge from B to A fades away,there is induced a rush from C to D in the same direction. It would seem also that the direct induced rush from C to Dis the more violent of the two, for the reason that the cessation ofthe inducing discharge in B A is more abrupt than its commence-ment. The inducing current is called the primary ; the inducedis called the secondary current. Experimeiils.—In the figure, X represents a screen of card or of glass, onthe further side of which is tixed a primary spiral of wire through which aLeyden jar discharge can be passed. On the nearer side of the screen is fixed. Fig. ii. another, secondary, spiral of wire, parallel to the other but separated from itby the glass or card. The ends of this last wire are connected with the endsof a wire coiled round a tube, C D. Then, by placing steel needles inside the tube C D, we can [by the resultsobtained in the last section] examine the direction of the current induced inthe secondary spiral. Thus, if the end P of the needle were found to be anorth pole, it would mean that the current passed in the general direction from o6 ELECTRICITY CH VI. P to Q ; since then, if one swam with the current and looked at the needle,the north pole would be to the left {see the rule given in last section). We shall find that when there is no break in the secondary circuit there isa weak magnetising action making the end P the north pole. This implies atotal magnetising action as of a current in the opposite direction to that in theprimary circuit. Without further experiment this would indicate merely aweak inverse current in
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