Reactance, resistors/resistance

The reactance describes the part of the system that behaves as a capacitor or inductor while the resistance term describes the part of the system that behaves as a resistor. The magnitude of the impedance is determined by the square root of the stun of the squares for the resistance and reactance [19] ... 

Precision wire-wound resistors are used for critical applications in which low noise and resistance stability are important, but since they are coils, they have an inductive reactance that must be taken into account for ac circuits. By folding the insulated wire in the middle and carefully forming parallel windings, the inductive component can be reduced by about a factor of 100. Precision standard resistors with an accuracy of about 50 ppm in the range of 1 fl to 10 Mfl are available from Electro Science Industries and other companies. These are often combined in the form of decade resistance boxes to provide a wide range of fixed values. 

In addition to secondary resistance control, other devices such as reactors and thyristors (solid-state controllable rectifiers) are used to control wound-rotor motors. Fixed secondary reactors combined with resistors can provide very constant accelerating torque with a minimum number of accelerating steps. The change in slip frequency with speed continually changes the effective reactance and hence the value of resistance associated with the reactor. The secondary reactors, resistors, and contacts can be varied in design to provide the proper accelerating speed-torque curve for the protection of belt conveyors and similar loads. 

Output voltage is linearly related to the plate separation x (equation (2.25)). A high-frequency source (e.g. 50 kHz) V,(icu) is used. The circuit produces an amplitude-modulated output voltage yo(i< ). The mean value of Vo(icu), proportional to j , is determined by demodulation and low-pass filtering (10 kHz corner frequency). In order to provide bias current for the amplifier (which should be an FET op amp), a discharge resistor R must be connected in parallel with Cx- The value of the feedback resistance should be high with respect to the reactance of C. ... 

Figure 5.24a shows a circuit that includes resistance, inductive reactance, and capacitive reactance. The phasor diagram is shown in Fig. 5.24b. The voltage phasor is the-sum of the phasors of the individual voltages. The maximum and instantaneous voltages are presented as capital V and small v, respectively. The instantaneous voltages, V, Vr, Vl, are projections on the horizontal axis in Fig. 5.24b of Fr, Fl, and Fc phasors. The potential difference between the terminals in Fig. 5.24 is in phase with the current in the resistor where the voltage maximum value is Fr = IR.

In a real application, the variable resistance R in the example can be replaced with an active device such as an FET. For an FET to function properly, it must act like a variable resistance. This happens in the FET, for example, as the dynamic drain resistance is placed in parallel with the load resistor R4 as illustrated in Fig. 12.41. The capacitive reactance of C2 determines the amount of phase shift that occurs with the overall variable resistance of the FET. This example is one of the most simple types of phase modulators. 

On page 99 of the Capacitors chapter, the concept of reactance was explained. This is a sort of effective resistance for a capacitor in an ac circuit, and its symbol is Xq. Since the RC filter is similar to a potentiometer with a pair of resistors... 

But what is the frequency that is indicated by the mysterious "1" value It depends on R and C. This diagram is only correct for cases where R of the resistor and the "effective resistance" (the reactance, Xq) are equal. (However, it... 

Impedance in a Series RC Circuit The impedance Z of an KC circuit is made up of two components the resistance of the resistor and the reactance of the capacitor. Because of the phase shift with the latter, however, the two cannot be combined directly but must be added vectorially, as shown in Figure 2-10. Here the phase angle for R is chosen as zero. As we have shown, the phase angle for a pure capacitive element is -90°. Thus, the X - vector is drawn at a right angle to and extends down from the R vector. From the Pythagorean theorem, the quantity Z. called the impedance, is given by... 

If a material has a pure electric resistance property, it is considered an ohmic material and has a constant resistance R largely independent of the potential applied or the current passed through. Other materials that do not comply with Ohm s law have non-linear resistances. Ideal resistors are considered to have no function in storing energy via an electric or magnetic field. However, in AC applications, this is hardly the case because an equivalent inductance or capacitance in series with the resistor element is often considered. The use of AC circuits requires the consideration of additional opposition to current flow due to electrical and magnetic fields treated as electrical reactance effects. An electrical circuit s impedance is defined by the sum effect of resistance and resistance [3]. 

An electrical equivalent circuit model, composed of a resistor and a capacitor which were connected in series, was adopted to represent the soymilk-electrode system. High frequency impedance measurements presented an increase in resistance and constant value in reactance for different coagulation times. This resistance is attributed to the bulk resistance of soymilk mixture and changed minimally when the coagulation process is finished [50]. 

The impedance of a battery can best be represented with the Randles model. Figure 8.7 illustrates the basic model of a lead acid battery that includes resistors R1 and R2 and capacitor C. (Inductive reactance is commonly omitted because it plays a negligible role.) Resistive-based testers look mainly at Rl, a value that increases with age but does not necessarily correlate with capacity. 

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