TY - JOUR
T1 - Effects of self-induction in iron cylinder
JF - Proceedings of the Royal Society of London. Series A
JO - Proc R Soc Lond A Math Phys Sci
SP - 22
LP - 27
M3 - 10.1098/rspa.1906.0054
VL - 78
IS - 521
AU -
Y1 - 1906/07/21
UR - http://rspa.royalsocietypublishing.org/content/78/521/22.abstract
N2 - If a solid cylindrical conductor be divided into imaginary concentric tubular conductors, the ordinary self and mutual induction theory shows that when the conductor is subjected to an alternating potential difference, the interior shells carry electric currents of smaller density than the exterior ones, and the currents suffer a phase displacement greater the nearer the centre of the cylinder. The theory shows that the permeability and conductivity of the material play an important part, the effects above mentioned being increased in magnitude with increasing permeability and conductivity. When, however, the material of the conductor has variable permeability the problem becomes more complicated, and it is the object of this paper to examine more closely what goes on in an iron cylinder when electric currents are reversed in it, and maintained steady after reversal. A second part of this research will deal with alternating currents of varying frequency and wave-form. The cylinder employed is of mild steel and has a diameter and length each equal to 10 inches (25.4 cm.). It is provided with holes drilled in a plane containing its axis of figure in such a manner that exploring coils can be threaded to inclose certain portions of that plane. The exploring coils are three in number. They are each 2 inches wide in a direction parallel with the axis of figure and midway between the ends of the Cylinder. Their depths in a radial direction are 1, 2, and 2 inches, and their average radii are 0.5, 2 and 4 inches respectively. These coils are referred to as Coils Nos. 1, 2, and 3, No. 1 being near the centre of the cylinder. The cylinder has been already described, but for the purpose of the present research has had a hole ¼-inch diameter drilled through it coinciding with the axis of figure. At each end of the cylinder are two massive gunmetal projections, which in the present research serve to conduct the electric current into the cylinder. The conductors attached to these projections are connected to a reversing switch so constructed that at its mid position it short-circuits the circuit of the cylinder and its conductors, which were arranged in the form of a circle about 6 feet diameter. The electric current was supplied by storage cells through an adjustable resistance and the shunt of an ampère-meter. The potential difference of the cells and the adjustable resistance were such that on reversing the current in the cylinder its value in the main circuit remained constant. In fact, the reversal of the main current was practically instantaneous. The epoch of reversal was noted on a seconds clock and at two-second intervals after reversal the deflections of the dead-beat galvanometers in circuit with the exploring coils were noted. The deflections have been reduced to volts per turn per square centimetre of the coils from which they were obtained, and plotted in terms of the time. Figs. 1, 2, and 3 give the results obtained from Coils Nos. 1, 2, and 3 respectively, and each curve is numbered to correspond with the total amperes reversed when it was observed. The curves have been integrated in order to find the maximum average value of the induction density B for the respective coils. The average values are set out in Table I.
ER -