Electrical, Electromagnetic and Magnetic.Effects

In investigation, at USBurMines (Ref 1), of various phenomena accompanying the detonation, it had been observed, initially, that electrical potentials were induced in single- and three-turn loops of wire around 

In the ProgrRept Jan-March 1952 tests using Alnico V magnets of various sizes were 

In one set of experiments, the impulse was transmitted to the magnet thru brass or stainless steel buffers. The waveforms produced were nearly ideal and consisted of a small potential rise and fall followed by a polarity reversal. Short-duration photographs of these phenomena were taken but not included in the rept 

In the Prog Rept July-Sept 1959 the following brief resume of work done up to July 1952 is given Currents were induced 

A series of supplemental tests were made on chges comprised of a confined cylindrical 3/4-inch diam Tetryl pellet over which a square metal duct or tube was placed, with an oversize 1-5/8-inch diam pellet placed at each end as confinement for the shock tube then the assembly end was initiated. These tests were made to det the fragment pattern effect using the tubes with or without fins. 

---

Detonation (and Explosion), Magnetic Effects Accompanying It. See under Detonation (and Explosion), Electrical, Electromagnetic and Magnetic Effects Accompanying It... 

Detonation (and expln), electrical, electromagnetic and magnetic effects accompanying it 4 D258... 

Electric and magnetic effects have been observed since ancient times without suspecting a close relationship between the two phenomena, and certainly not inferring any close connection with visible light. The modern view is that the three effects are different aspects of a single concept, known as the electromagnetic field, which in turn is a manifestation of interactions involving the elementary entities called electrons and photons. 

A distinction must be made between gravitational effects for which the presence of material in the field does not change the intensity of the field, and the electrostatic and magnetic effects for which the presence of material within the field does alter the intensity. A complete treatment of electrostatic and magnetic effects would require a discussion of electromagnetic theory and the use of Maxwell s equations. However, we wish only to illustrate the thermodynamic effects of electric and magnetic fields. We therefore accept the results of a complete treatment and apply the results to simple systems. 

Here, oto(T,V) and xo(T,V) represent, respectively, the modified scalar electric polarizability and magnetic susceptibility As before, we assume that these parameters do not depend on the intensity of the applied electromagnetic field such materials are said to be linear in their response to electromagnetic fields. Phenomena such as ferroelectricity and ferromagnetism are thus excluded from the current formulations, as are effects achieved in high intensity fields, for which higher powers in o and IKo are needed. 

Once the primary electron beam is created, it must be demagnified with condenser lenses and then focused onto the sample with objective lenses. These electron lenses are electromagnetic in nature and use electric and magnetic fields to steer the electrons. Such lenses are subject to severe spherical and chromatic aberrations. Therefore, a point primary beam source is blurred into a primary beam disk to an extent dependent on the energy and energy spread of the primary electrons. In addition, these lenses are also subject to astigmatism. AH three of these effects ultimately limit the primary beam spot size and hence, the lateral resolution achievable with sem. 

In 1821 Michael Faraday sent Ampere details of his memoir on rotary effects, provoking Ampere to consider why linear conductors tended to follow circular paths. Ampere built a device where a conductor rotated around a permanent magnet, and in 1822 used electric currents to make a bar magnet spin. Ampere spent the years from 1821 to 1825 investigating the relationship between the phenomena and devising a mathematical model, publishing his results in 1827. Ampere described the laws of action of electric currents and presented a mathematical formula for the force between two currents. However, not everyone accepted the electrodynamic molecule theory for the electrodynamic molecule. Faraday felt there was no evidence for Ampere s assumptions and even in France the electrodynamic molecule was viewed with skepticism. It was accepted, however, by Wilhelm Weber and became the basis of his theory of electromagnetism. 

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. 

Another example of zero-point energy arises in the detailed quantum theory of the electromagnetic field, known as quantum electrodynamics. The empty vacuum with no photons present is actually the zero-point level with n = 0. The non-zero energy of this state cannot be measured directly, but does have some observable consequences. The vacuum is really a state of fluctuating electric and magnetic fields that are significant at the atomic level. Without them, there would be no mechanism for the spontaneous emission of photons from excited states. There also have very small effects on the energy levels of atoms (see Section 4.4). 

There is a cause-effect relationship between electric charge density and electric held, represented by Eq. (10). Since pe = 0, it should follow that E = 0. Such trivial solution, however, cannot possibly represent a photon. There is another alternative. Induction Eqs. (8) and (9) relate to E and B so that, if B were an independent variable, variations of magnetic held could, in principle, induce an electric held. However, magnetic held B is conventionally ascribed to moving charges [66]. Again, pe = 0 forbids B, and a fortiori E. It seems that there is some violation of causality an electromagnetic held represented by E and B (effect) without a source pe (cause). 

Electromagnetic interference (EMI) refers to the interaction between electric and magnetic helds and sensitive electronic circuits and devices. EMI is predominantly a high-frequency phenomenon. The mechanism of coupling EMI to sensitive devices is different from that for power frequency disturbances and electrical transients. The mitigation of the effects of EMI requires special techniques, as will be seen later. Radio frequency interference (RFT) is the interaction between conducted or radiated radio frequency helds and sensitive data and communication equipment. It is convenient to include RFI in the category of EMI, but the two phenomena are distinct. 

---