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Alternating Current (ac) Electronics
Published in Dale R. Patrick, Stephen W. Fardo, Electricity and Electronics Fundamentals, 2020
Dale R. Patrick, Stephen W. Fardo
Figure 2-3 shows several voltage values associated with ac. Among these are peak positive, peak negative, and peak-to-peak ac values. Peak positive is the maximum positive voltage reached during a cycle of ac. Peak negative is the maximum negative voltage reached. Peak-to-peak is the voltage value from peak positive to peak negative. These values are important to know when working with radio and television amplifier circuits. For example, the most important ac value is called the effective, or measured, value. This value is less than the peak positive value. A common ac voltage is 120 V, which is used in homes. This is an effective value voltage. Its peak value is about 170 V. Effective value of ac is defined as the ac voltage that will do the same amount of work as a dc voltage of the same value. For instance, in the circuit of Figure 2-4, if the switch is placed in position 2, a 10-V ac effective value is applied to the lamp. The lamp should produce the same amount of brightness with a 10-V ac effective value as with 10 V dc applied. When ac voltage is measured with a meter, the reading indicated is effective value.
Background
Published in Russ Martin, Sound Synthesis and Sampling, 2012
Electrons flow through a conducting medium if there is a difference in the distribution of electrons, which means that there is an excess of electrons in one location, and too few electrons in another location. Such a difference is called a potential difference, or a voltage. Voltage is measured with a unit called the volt. The higher the voltage, the greater the potential difference, and the more electrons that want to move from one location to another. If the potential difference gets large enough, then the electrons will jump through air (which is what a spark is: electrons flowing through air). Normally electrons only flow through metals and other conducting materials in a more controlled manner.
Electrical Power Systems/Improved Efficiency
Published in Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo, Energy Conservation Guidebook, 2020
Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo
These basic electrical relationships show that when voltage is increased, the current in the circuit increases in the same proportion (V = I × R). Also, as resistance is increased, the current in the circuit decreases (I = V/R). Also, the power converted by the circuit is equal to voltage times current (P = V × I). When an AC circuit contains only resistance, its behavior is similar to a direct-current (DC) circuit. Purely resistive circuits are seldom encountered in the design of electrical power systems, although some devices are primarily resistive in nature (such as resistive heating units).
Effect of salt and NAPL on electrical resistivity of fine-grained soil-sand mixtures
Published in International Journal of Geotechnical Engineering, 2018
Prabir K. Kolay, Sandeep Goud Burra, Sanjeev Kumar
The most popular methods to perform soil resistivity test are: (i) Wenner method, (ii) Schlumberger method and (iii) Dipole Dipole method. Fig. 2(a) shows an overall linear electrode configuration for a typical resistivity measurement where, current is delivered through the electrodes A and B, and voltage readings are made with electrodes M and N. All four electrodes are chosen to be in a straight line for simplicity. In general, the electrodes are not restricted to being collinear, although solving the electromagnetic field equations that accompany such arrays becomes more difficult. The AC current source is in series with an ammeter, which measures the total current I and going into the ground through the electrodes at points A and B. A voltmeter attached to the two electrodes at points M and N measures the potential difference V between these points. By convention, the electrodes at the four surface points (A, M, N, B) are also named (A, M, N, B). The ratio (V/I) obtained is the apparent resistance for the entire subsurface (Herman 2001; Reynolds 1997). There are several ways in which the electrodes in Fig. 2(a) may be arranged, with the spacing chosen to match the needs of a particular survey site. Some of these arrangements are pictured in Fig. 2(b) i.e. Wenner array (ASTM G 57–06 2012), Schlumberger arrays (ASTM D 6431–99 2010) and dipole–dipole array (ASTM D 6431–99 2010). Each of these electrode configurations has its own advantages and disadvantages, depending on the type of survey to be performed.