Owner: Openticle URL:http://openticle.com Join Date: Tue, 11 Dec 2007 07:55:25 -0600 Rating:0 Site Description: Open Article : Free science and engineering article online Site statistics:Click here
Magnetic Materials 2008-05-23 23:43:21 Magnetic materials are those materials that can be either attracted or repelled by a magnet and can be magnetized themselves. The most commonly used magnetic materials are iron and steel. A permanent magnet is made of a very hard magnetic material, such as cobalt steel, that retains its magnetism for long periods of time when [...] Read more:Materials
Magnetomotive Force 2008-05-25 23:37:14 Magnetomotive force (mmf) is the strength of a magnetic field in a coil of wire. This is dependent on how much current flows in the turns of coil: the more current, the stronger the magnetic field; the more turns of wire, the more concentrated the lines of force. The current times the number of turns [...] Read more:Force
Magnetic Field and Polarity of a Coil 2008-05-25 22:39:18 Bending a straight conductor into a loop has two results: (1) magnetic field lines become more dense inside the loop, and (2) all lines inside the loop are aiding in the same direction. When a conductor is shaped into several loops, it is considered to be a coil. To determine the polarity of a coil, [...] Read more:Field
Electromagnetism 2008-05-24 23:12:15 Electromagnetism
The relationship between magnetism and electrical current was discovered by a Danish scientist named Oersted in 1819. He found that if an electric current was caused to flow through a conductor, the conductor produced a magnetic field around that conductor (Figure 21).
Polarity of a Single Conductor
A convenient way to determine the relationship between the current [...]
Field Intensity 2008-05-27 23:41:33 When a coil with a certain number of ampere-turns is stretched to twice its length, the magnetic field intensity, or the concentration of its magnetic lines of force, will be half as great. Therefore, field intensity depends on the length of the coil. Equation (1-14) is the mathematical representation for field intensity, which is related [...] Read more:Field
, Intensity
Reluctance 2008-05-30 04:24:51 Opposition to the production of flux in a material is called reluctance, which corresponds to resistance. The symbol for reluctance is R, and it has the units of ampere-turns per weber (At/wb). Reluctance is related to magnetomotive force, mmf, and flux, F, by the relationship shown in equation (1-15).
Reluctance is inversely proportional to permeability (μ). [...]
Magnetic Circuits 2008-06-02 00:10:09 A magnetic circuit can be compared with an electric current in which EMF, or voltage, produces a current flow. The ampere-turns (NI), or the magnetomotive force (Fm or mmf), will produce a magnetic flux F (Figure 26). The mmf can be compared with EMF, and the flux (Φ) can be compared to current. Equation (1-16) [...] Read more:Circuits
B-H Magnetization Curve 2008-06-03 17:59:35 BH Magnetization Curve
The BH Magnetization Curve (Figure 27) shows how much flux density (B) results from increasing the flux intensity (H). The curves in Figure 27 are for two types of soft iron cores plotted for typical values. The curve for soft iron 1 shows that flux density B increases rapidly with an increase in [...]
Hysteresis 2008-06-04 21:23:00 When current in a coil reverses direction thousands of times per second, hysteresis can cause considerable loss of energy. Hysteresis is defined as “a lagging behind.” The magnetic flux in an iron core lags behind the magnetizing force.
The hysteresis loop is a series of curves that shows the characteristics of a magnetic material (Figure 28). [...]
Magnetic Induction 2008-06-06 23:20:26 Electromagnetic induction was discovered by Michael Faraday in 1831. Faraday found that if a conductor “cuts across” lines of magnetic force, or if magnetic lines of force cut across a conductor, a voltage, or EMF, is induced into the conductor. Consider a magnet with its lines of force from the North Pole to the South [...] Read more:Induction
DC Sources - DC Generator 2008-06-12 21:16:47 DC Generator
A simple DC generator consists of an armature coil with a single turn of wire. The armature coil cuts across the magnetic field to produce a voltage output. As long as a complete path is present, current will flow through the circuit in the direction shown by the arrows in Figure 2. In this [...]
DC Sources - Batteries 2008-06-12 21:14:26 Batteries
A battery consists of two or more chemical cells connected in series. The combination of materials within a battery is used for the purpose of converting chemical energy into electrical energy. To understand how a battery works, we must first discuss the chemical cell. The chemical cell is composed of two electrodes made of different [...]
Full-Wave Rectifier Circuit 2008-06-16 02:54:44 Full-Wave Rectifier Circuit
A full-wave rectifier circuit is a circuit that rectifies the entire cycle of the AC sine-wave. A basic full-wave rectifier uses two diodes. The action of these diodes during each half cycle is shown in Figure 7.
Another type of full-wave rectifier circuit is the full-wave bridge rectifier. This circuit utilizes four diodes. These [...]
Half-Wave Rectifier Circuit 2008-06-16 02:44:21 Half-Wave Rectifier Circuit
When a diode is connected to a source of alternating voltage, it will be alternately forward-biased, and then reverse-biased, during each cycle of the AC sine-wave. When a single diode is used in a rectifier circuit, current will flow through the circuit only during one-half of the input voltage cycle (Figure 6). For [...]
DC Sources - Rectifier 2008-06-16 02:42:15 Rectifiers
Most electrical power generating stations produce alternating current. The major reason for generating AC is that it can be transferred over long distances with fewer losses than DC; however, many of the devices which are used today operate only, or more efficiently, with DC. For example, transistors, electron tubes, and certain electronic control devices require [...]
Thermocouples 2008-06-16 02:39:10 Thermocouples
A thermocouple is a device used to convert heat energy into a voltage output. The thermocouple consists of two different types of metal joined at a junction (Figure 3).
As the junction is heated, the electrons in one of the metals gain enough energy to become free electrons. The free electrons will then migrate across the [...]
Series-Paralel Circuit 2008-06-16 23:34:45 Series Circuit
A series circuit is a circuit where there is only one path for current flow. In a series circuit (Figure 16), the current will be the same throughout the circuit. This means that the current flow through R1 is the same as the current flow through R2 and R3.
Parallel Circuit
Parallel circuits are those circuits [...]
Electric Circuit 2008-06-16 23:18:18 Electric Circuit
Each electrical circuit has at least four basic parts: (1) a source of electromotive force, (2) conductors, (3) load or loads, and (4) some means of control. In Figure 13, the source of EMF is the battery; the conductors are wires which connect the various component parts; the resistor is the load; and a [...] Read more:Electric
Temperature Coefficient of Resistance 2008-06-16 23:09:21 Temperature Coefficient of Resistance
Temperature coefficient of resistance, α (alpha), is defined as the amount of change of the resistance of a material for a given change in temperature. A positive value of α indicates that R increases with temperature; a negative value of α indicates R decreases; and zero α indicates that R is constant. [...] Read more:Temperature
Resistivity 2008-06-16 22:50:08 Resistivity is defined as the measure of the resistance a material imposes on current flow. The resistance of a given length of conductor depends upon the resistivity of that material, the length of the conductor, and the cross-sectional area of the conductor, according to Equation (2-1).
The resistivity ρ (rho) allows different materials to be compared [...]
DC Circuit Terminology 2008-06-16 22:37:08 Schematic Diagram
Schematic diagrams are the standard means by which we communicate information in electrical and electronics circuits. On schematic diagrams, the component parts are represented by graphic symbols, some of which were presented earlier in Module 1. Because graphic symbols are small, it is possible to have diagrams in a compact form. The symbols and [...] Read more:Circuit
Recommend Site To A Friend
