14 Faraday Induced current

Alternating-current motors are classified as induction motors or synchronous motors. Faraday found that a stationaiy wire in a magnetic field produced no current. However, when the wire continues to move across magnetic lines of force, it produces a continual current. When the motion stops, so does the current. Thus Faraday proved that electric current is only produced from relative motion between the wire and magnetic field. It is called an induced current—an electromagnetic induction effect. 

To obtain a mass spectrum, ions need to be converted into a usable signal by a detector. The simplest form of ion detection is a photographic plate or a Faraday cup for the direct measurement of the charge. In a Faraday cup the induced current is generated by an ion which hits the surface of a dynode and emits... 

With an increase of the magnetic permeability, the interaction between currents in accord with Faraday s law increases and curves of distribution of induced currents, shown in Figs. 2.4-2.5 for both quadrature and inphase components, are shifted to the range of lower frequencies. 

Ever since the discovery of the voltaic pile, there had been doubt about the identity of voltaic and common (i.e. frictional) electricity. In 1831 Faraday made his classic discovery of electromagnetic induction, and thus added a third type of electricity. The first experiment Faraday performed after he had discovered the induced current was to see if it would produce any decomposition in a drop of copper sulphate solution. The quantity of electricity passed was too small to produce any... 

This point seems to have occurred to Faraday on the first day of his discovery of electro-magnetic induction for he tried to obtain electro-chemical decomposition of a solution of copper using induced electricity (17). By showing that electricity from whatever source produced the same effects, the identity of the causal electricities would be established. This had been the standard method during the first three decades of the nineteenth century and Faraday saw no need to alter it. He was quite elaborate in his arrangement to produce electro-chemical decomposition from induced electricity. He realised that when he broke the circuit the electric current flowed in the opposite direction and this would cancel out the electro-chemical effect of the original induced current. So before he broke the circuit he removed the pole from the solution of copper. He repeated this process many times, but found no electrochemical decomposition. 

A lengthy solenoid in which circulates a variable current Is(t) as a function of time, generates a variable magnetic field and induces an electric field satisfying Faraday s law ... 

If one of the metals (commonly referred to as superconductors) is castin the form of a ring and an external magnetic field is applied perpendicularly to its plane and then removed, a current will flow round the ring induced by-Faraday induction. This current will produce a magnetic field, proportional to the current, and the size of the current may be observed by measuring dm field. Were the ring (e g., one made of lead) at a temperature above 7.2 K, this current and field would decay to zero in a fraction of a second. 

We also observe rather thankfully, that all the laws of nature bear each other out. There is no contradiction whichever way we look at the situation. For example, even though the current in the inductor is subsequently higher, its rate of change is less, and therefore, so is the induced voltage (on the basis of Faraday s/Lenz s law). And this allows for the additional drop appearing across the resistor, as per Kirchhoff s voltage law ... 

Bulk Velocity. Electromagnetic Flowmeters. An electromagnetic flowmeter is based on the principle of electromagnetic induction as expressed by Faraday s law. An electric current is induced in a conductor when it moves across a magnetic field. The flowmeter consists of a pair of electrodes placed diametrically opposite one another on the same section of pipe (Figure 23). A conductive slurry flowing through the... 

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