Mutual Induction and the Internal Resistance of a Voltaic Cell

The usual method of making a rapid determination of the internal resistance of a voltiac cell, primary or secondary, is by means of the condenser in circuit with a ballistic galvanometer. The deflection of the galvanometer due to the discharge of the condenser is first taken on open circuit with the cell and again when the cell is on a closed circuit the known resistance. The working formula is r=d—d1 over d1xR, in which d and d1 are the different deflections of the galvanometer needle and R is the external resistance of the closed circuit. The explanation of this method can be found in Carhart and Patterson\u27s Electrical Measurements

Nucleations According to Barus

No doubt all students of science have read more or less about Barus\u27 work on condensation phenomena as produced in a specially constructed fog chamber. As is known, his work has been done under the direction of the Carnegie Institution of Washington, founded particularly for the solution of research problems, involving much time and considerable expense. The prime purpose of his work, so far as I can interpret it, is to determine the part played by various kinds of nuclei in the atmospheric condensation of vapor. This, of course, is a very interesting problem to the student of physiography, as well as to the physicist

The Magnetic Effect of an Electric Current

From a practical point of view, the magnetic property of an electric current is of great value to man. It is this property that is utilized in the dynamo for the generation of large currents of electricity. It is also this property that enables man to utilize the driving power of the electric motor in the manufacturing industries

Hydrostatics

The classroom apparatus necessary for an effective, interesting presentation of hydrostatics includes: pressure tubes, manometer tubes, pressure syringe, Pascal\u27s vases and equilibrium tubes. All of these are listed in the apparatus catalogs found in every high school

Motion

Motion is a general property of matter. There is no rest in the absolute sense. An object at rest with reference to the earth \u27s surface is in rapid motion with reference to the earth\u27s axis of rotation just as a person may be at rest in a Pullman car and at the same time be in rapid motion with reference to the ground. All divisions of matter, - masses, molecules, atoms, protons, and electrons are moving relatively all of the time

The Simple Machines

With reference to a pulley system, the work equation is clearly discerned in its practical operation. In presenting the pulley, the writer uses a rectangular frame about two feet high and three feet wide. A number of hooks are screwed into the top cross piece of the frame. With such a device a number of different pulley combinations can be shown at one time

Current Induction

The modern transformer, now quite generally used in the commercial distribution of electrical power in the cities of the world, ranks next to the dynamo in importance in the electrical world. The transformer is an invention which embodies. the practical application of Faraday\u27s first experiment in current induction, in which a closed iron ring carrying a primary coil and a secondary coil was used