The Measurement of Magnetic Hysteresis . arge resistance of 240 for this uncertainty we may say that the current is reversed in several stepswhich (except possibly those occurring in the uncertain part of the motion) are notsudden because of the great self-induction of the choking coil (§ 33). Though (witha possible exception) there is no sudden change in the current, the rate of variation ofthe current is no doubt much greater at some stages of the change than at others. The key generally worked w^ell; it was, however, subject to slight uncertainties. § 32. A fifth key was designe
The Measurement of Magnetic Hysteresis . arge resistance of 240 for this uncertainty we may say that the current is reversed in several stepswhich (except possibly those occurring in the uncertain part of the motion) are notsudden because of the great self-induction of the choking coil (§ 33). Though (witha possible exception) there is no sudden change in the current, the rate of variation ofthe current is no doubt much greater at some stages of the change than at others. The key generally worked w^ell; it was, however, subject to slight uncertainties. § 32. A fifth key was designed in 1900. Our aim was to ensure that the primarycircuit should never be broken, and also that the resistances introduced into thecircuit should be as small as possible, so that the rate of change of the current should,at every part of its variation, be as small as possible. The battery is connected through the Weston ampere-meter, WA (fig. 5), with theterminals g, h on an ebonite arm working about a pivot at 0. The terminals g, h are. Fig. 5. connected to two brass springs, k, I, one at each end of the arm. These springs sUdeover a series of sectors a, 6, c, d, e, cut out of a brass ring. The sectors a and h and VOL. —Ao 1 58 MESSES. G. F. G. SEARLE AND T. G. BEDFORD the sectors d and« e are connected by the resistance coils D, D, while the sector c isinsulated. The spaces between the sectors^ about 1*5 millims. wide, are filled withebonite so that the springs pass smoothly over thera. The primary circuit PC joinsthe sectors a, e. The two stops s, ,s^ arrest the motion of the arm when I has got wellon to either a or 6, so as to be clear of h or cL To avoid any possible break in passingfrom one sector to the next, the spring I is made in two portions, l^, ?2, ©ach of whichpresses upon the sectors. The spring k is arranged so as to touch the sectors onlyat its ends, hi, h^. The lengths of the sectors and of the springs are arranged so thatthe key performs the reve
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