AC source

The electrical power supplied to electrical motors can be from a direct-current (dc) source or an alternating-current (ac) source. Because dc motors are more... 

Measurement of the conductance of an electrolyte solution using an ac source. Rate of change of conductance as a function of added titrant used to determine the equivalence point. 

Platinum electrodes low-potential ac source conductance bridge. 

Fig. 11.3. The influence of the input capacitance on output noise. To make a simple estimation, the input noise of the op-amp is represented by an ac source at the noninverting input end. The smaller the input impedance, the larger the noise at the output end. Therefore, the input capacitance generates a large high-frequency noise.

The source is an AC source with a magnitude of 10 volts and a phase of 37 degrees, 10Z370 in phasor notation. This magnitude can be interpreted as either peak or RMS. If you specify 10Z37° as the magnitude of the source, and the number... 

When you are finding output impedance you must set the input AC source to zero. Since the input is a voltage source, we... 

Next we need to add an AC source at the output to measure the impedance. We could use either an AC voltage source or an AC current source. If you use a voltage source, wire the circuit shown below ... 

Capacitor C2 is necessary to preserve the bias of the amplifier. Remember that V3 is an AC source. For biasing, all AC sources are set to zero. Since V3 is a voltage source, it would be replaced by a short. Without C2, the source terminal of the jFET would be grounded when calculating the bias. This would destroy the bias and render the impedance measurement invalid. 

Since the gain is VoA/ln and Vltl is a 1-volt magnitude AC source, the magnitude of the gain is just the magnitude of VO ... 

Diffraction patterns from a nickel-alumina steam reforming—methanation catalyst and a sample of sintered nickel recorded on a LIN AC source... 

Direct evidence for a spin density wave transport is the detection of a current oscillating at a frequency that is proportional to the dc current carried collectively. The recent observation of such oscillations the harmonic and subharmonic locking of this oscillation to an external ac source and a motional narrowing of the NMR spectrum in the sliding SDW state have established firm evidence for the existence of a novel collective transport in a SDW condensate. 

A suitable method for measuring the conductivity of glass melts up to 1450 °C has been described by Stanck et al. (1965). An AC source of 800 Hz frequency was used in order to eliminate polarization, and platinum electrodes were employed. The results obtained with several types of industrial glasses are shown in Fig. 58. Their compositions are listed in Table IJ. 

The lamps may be operated on AC or DC, but for polymerisation studies and radical lifetime measurements DC must be used. For a low-pressure lamp the intensity falls to nearly zero 120 times per second for a 60 cycles AC source " the high-pressure lamp also tends to be unstable with AC . Circuits (Fig. 35) are shown for medium-pressure and high-pressure lamps operating procedures are given quite clearly in these last two references. The low-pressure lamp reaches stable operating conditions quite quickly, but the other two types require some time to do so (10-15 min). The high-pressure lamp also has a very short lifetime. 

Fig. 13.19 SEM images of the gap electrodes (a) the initial electrode pairs with the spacing of 5 mm fabricated by conventional photolithography (b) the nanogap with a separation of 56 nm obtained at an ac sources frequency/= 260 Hz and the series resistances Rj=R = 0. kV (c) the nanogap with a separation of 28 nm obtained at/= 260 Hz and Rj = R = kV (d) the nanogap with a separation of 9 nm at/=820 Hz and R = R = kV. Reprinted with permission from ref. [125]. Copyright 2005, American Institute of Physics...

Their locaticm is a trial and error process which requires a VOM and a low voltage AC source. This can be deadly if you don t know what you re doing. 

This operation determines the values of R and C that, in series, behave as the cell does at the measurement frequency. The impedance is measured as a function of the frequency of the ac source. The technique where the cell or electrode impedance is plotted V5. frequency is called electrochemical impedance spectroscopy (EIS). In modem practice, the impedance is usually measured with lock-in amplifiers or frequency-response analyzers, which are faster and more convenient than impedance bridges. Such approaches are introduced in Section 10.8. The job of theory is to interpret the equivalent resistance and capacitance values in terms of interfacial phenomena. The mean potential of the working electrode (the dc potential ) is simply the equilibrium potential determined by the ratio of oxidized and reduced forms of the couple. Measurements can be made at other potentials by preparing additional solutions with different concentration ratios. The faradaic impedance method, including EIS, is capable of high precision and is frequently used for the evaluation of heterogeneous charge-transfer parameters and for studies of double-layer structure. 

---