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This may be used as an inductive resistance by connecting the alternating circuit to primary post No. 1 and secondary No. 1 and connecting by plugs coils 2, 3 and 4 with switches A and B both on 1. By changing switch A to 2, one coil is cut out, changing to 3, two coils are out, changing to 4, three coils are out. All four coils may be cut out by placing both switches on contact No. 1 and connecting coils 1 and 2.

The four parts of the other coil (b. Fig. 1) are so connected as to make it the stator of a small induction motor. The two opposite coils are so connected that they will produce like poles in the same

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direction at the same time; that is, they oppose each other. These are connected to the alternating circuit through a non-inductive resistance. The other two coils are joined in like manner and connected with the same circuit through the inductive resistance above described. These connections are shown in Fig. 3. This inductive resistance will produce such a lag of the current in that circuit as will make the magnetic field a rotating one. This rotating field may be shown by placing within the coil, the block with a small iron bar supported on top, shown in Fig. 1. The bar is pulled around by the rapidly rotating field. When its rate becomes the same as the field, either circuit may be disconnected and the bar will continue to rotate in synchronism with the field.

An alumnium siren supported on a pivot just above the coil may be made to rotate at any desired speed by varying the current; it will rotate much more rapidly if a piece of sheet iron is held just above the

siren.

By removing the block, the small squirrel cage armature shown in Fig. 1 may be placed within the coil. It will rotate rapidly, illustrating the principle of the induction motor. If a four-inch watch glass be

placed on top of the coil and any kind of metal ball be placed on this glass it will rotate.

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By filling the shell of a hen's egg with iron filings and placing it on this glass, an amusing experiment may be given. At first it begins

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to rotate on its side or on its shorter axis, but after attaining a certain

velocity it will stand up and rotate on the end. It is perhaps unnecessary to say that the same experiments may be performed by using in place of the inductive resistance the same apparatus as a step down transformer.

NOTE. The Scientific American of May 6, 1906, has a valuable article on this subject.

THE ENTRANCE REQUIREMENT IN PHYSICS AND ITS RELATION TO THE PHYSICS OF THE COLLEGE COURSE

PROFESSOR N. F. SMITH, OLIVET COLLEGE

A conference such as this, composed of representatives from the university, the colleges and the secondary schools, seems to be a peculiarly appropriate place to discuss a question directly affecting our mutual relations. I know that the subject of the college entrance requirement in physics is an old one, but educational conditions in schools and colleges are changing so rapidly as to warrant the reconsideration of some aspects of this theme. My subject seems naturally divided into three parts, which I wish to consider in order.

1. Should physics be a required subject for admission?

I think the time has come when all of us are ready to admit that those subjects form the best basis for entrance to college which give the best preparation to the students whose education is finished with the high school course. My question might therefore be put in the form: "Should physics be a required subject in the high school course?" In this day when the elective system has been allowed to run riot through our courses of study there is a tendency to make practically all subjects optional, both in school and college. Whatever may be said in favor of such a system in the college or university, and I believe myself that it is very little,-these arguments certainly do not apply to the high school where the pupils are far too immature to make a choice of subjects on any rational basis. Some subjects then should be prescribed as required of all students in the high school course. Among these should be a certain amount of science work, and among the sciences, it seems to me there are strong reasons for selecting physics.

These reasons are chiefly as follows: (a) Physics is a dicsiplinary study comparable to mathematics or Latin, and possesses this characteristic perhaps to a greater degree than any of the other sciences of the high school course. (b) The principles of physics are fundamental, underlying the other sciences and forming a proper basis for their study. (c) A knowledge of the elements of physics is essential to any

intelligent understanding of the great forces in constant use in everyday life.

From the college point of view, then, it would seem that physics should be a required subject for admission quite as much for the sake of those students who do not go to college as for those who do, since making physics a requirement for college entrance will tend to keep it a requirement in the high school course. In opposition to this view, objections based on local conditions of expediency are sometimes urged. A high school is pointed out which is equipped, either in teaching force or apparatus or both, to do good work in chemistry, but is poorly equipped for work in physics. We are asked whether it is not better for that school to continue its course in chemistry and not undertake the work in physics. My answer is yes, if it cannot do both in a satisfactory manner. But that is not a reason why the general principle should be changed or why the college should change its entrance requirement. A somewhat similar objection is based on the expense involved in providing equipment for proper instruction in physics, which perhaps exceeds that required for the other sciences. I shall refer to this more fully under the next division of my subject, but I wish to say here that the few hundred dollars' expense initially involved is insignificant when any educational principle is at stake, and, secondly, that the great mistake of the small high schools seems to me to be the attempt to include in their curriculum all of the sciences instead of concentrating their energies and their resources upon one or two. Let the small high school with only three or four teachers gave up the attempt to teach zoology, botany, physiology, physics, chemistry, and what not, and perfect a thorough course in one or two of these subjects and the expense will be no more and the educational results far better.

My last reason for urging physics as an entrance requirement is one based on the desirability for uniformity in this matter. Physics is of course accepted as an entrance subject by all the colleges. There seems to be a growing tendency to make it a required subject. Especially is this true in our own state where it is required by the University of Michigan, Olivet, Hillsdale, Kalamazoo, Adrian, and Hope. It seems to be optional at Alma and Albion,-the latter specifying in the science requirement, "physics preferred."*

It may well be asked why, if physics is already required by practically all the Michigan colleges, it is necessary to discuss this phase of the subject. I reply, to emphasize the importance to the smaller high schools concentrating their attention upon this one science, not merely because it is a required subject for admission to college, but because it is best for the educational development of their pupils that this one

*Physics is now required for admission to Albion College.

science should be taught well rather than that several sciences should be taught indifferently.

2. If physics is presented as an entrance subject, what should constitute a unit course? Here again I wish to emphasize the fact that the sort of a course which seems desirable as a preparation for college differs in no way from the course which is best for the students who do not go to college. It is true, however, that the requirements of the colleges and particularly of the State University, have had and will always have a tremendous influence in determining the character of the courses offered in the high schools. No fountain rises higher than its source, and the source of the teaching in the high schools is the University and the colleges. The standard of this teaching is largely determined by the minimum entrance requirements of these institutions. If the Michigan colleges have taken the lead in placing physics among the required subjects for admission, they are lamentably behind most other institutions in the character of the course which they require for college entrance. I do not, in this place, need to argue the importance of individual laboratory work on the part of the student as a part of the preparatory course in physics. Most of us would agree that this work should be chiefly quantitative in its nature and that a proper record of the experiments should be kept by the student. Nothing less han this is accepted as meeting the admission requirements by any college or university of the first rank, so far as I know, outside the state of Michigan. Nothing less than this is worthy of the high schools of this state where an attempt is made to present the subject. And yet in studying the catalogues and inquiring into the practice of the colleges of Michigan, I find great uncertainty or great deficiency on this point. This is due in large measure to the position taken by the University of Michigan, the natural educational leader in this

state.

I am pleased to note in the announcements of the last two years a distinct advance over the statement in the earlier catalogues of the University. The last announcement in defining the physics requirement says: "The course should include one period of laboratory work per week, throughout the year." This is better than the previous statement: "Laboratory work is earnestly advised but not required," but even the last statement is far too vague. Does the University require such work for admission? What does it regard as a satisfactory laboratory course? What means are taken to ascetrain the character of the student's laboratory work? These are questions which should be more explicitly defined.

Albion College admits without examination students from all schools approved by the University of Michigan, thus indorsing their standard. Kalamazoo defines her entrance requirements somewhat vaguely. An idea of what is considered acceptable may be gained by a reference to her own preparatory course. "Physics; Fourth year; fall

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