Conductors cross sectional area

Where K = 143 for EPR insulation and Amm is the smallest conductor cross-sectional area. 

Figure 3.2 shows the net flow of electrons in a conductor cross-sectional area A in the presence of an applied field E. Notice that the direction of electron motion is opposite to that of the electric field and of conventional current, because the electrons experience a coulombic force qE, in the X direction, due to their negative charge. We know that the conduction electrons are actually moving around randomly in the metal, but we will assume that, as a result of the application of the electric field E, they all acquire a net velocity in the x direction. Otherwise, there would be no net flow of charge through area A. 

If Eq. (21.22) is compared to Eq. (21.21), we see that the conductance of an electrolyte solution depends upon the types of irais (via z m,), their concentrations (c,), as well as the dimension of the imiic conductor (cross-sectional area A and distance between electrodes /) ... 

Conductor cross- sectional area Reference Method A (enclosed in conduit in an insulated wall, etc.) Reference Method B (enclosed in conduit on a wall or ceiling, or in trunking) Reference Method C (clipped direct) Reference Method E (on a perforated cable tray) or in free air OD D CO O (D... 

Conductor cross-sectional area (mm ) 1 Two-core cable, d.c. (mV/A/m) 2 Two-core cable, single-phase a.c. (mV/A/m) 3 Three- or four-core cable, three-phase (mV/A/m) 4... 

Type of conductor Conductor cross-sectional area (mm ) Cable factor... 

The cross-sectional area of the wick is deterrnined by the required Hquid flow rate and the specific properties of capillary pressure and viscous drag. The mass flow rate is equal to the desired heat-transfer rate divided by the latent heat of vaporization of the fluid. Thus the transfer of 2260 W requires a Hquid (H2O) flow of 1 cm /s at 100°C. Because of porous character, wicks are relatively poor thermal conductors. Radial heat flow through the wick is often the dominant source of temperature loss in a heat pipe therefore, the wick thickness tends to be constrained and rarely exceeds 3 mm. 

S = cross-sectional area of a bare ground conductor in mm . 

In smaller cross-sectional area,s of the current-carrying conductors of the distribution network, i.e. for low-capacity networks where R/Xl is high, series compensation may be redundant. 

Volume resistivity or specific resistance this is the resistance of a conductor of unit length and unit cross-sectional area. i.e. 

As discussed later, the enclosure of an IPB may carry induced currents up to 95% of the current through the main conductors. Accordingly, the enclosure is designed to carry longitudinal parasitic currents up to 90-95% of the rated current of the main busbars. The cross-sectional area of the enclosure is therefore maintained almost equal to and even more than the main conductors to account for the dissipation of heat of the main conductors through the enclosure only, unless an additional forced cooling system is also adopted. The outdoors part of the enclosure exposed to atmospheric conditions is also subjected to solar radiation. Provision must be made to dissipate this additional heat, from the enclosure. 

By definition, the resistivity and conductivity of a and cross-sectional area A conductor of length d... 

The series resistance of a transmission line is closely related to the losses that will be dissipated when current passes through the line (proportional to the square of the current magnitude). The resistance is proportional to the length of the line but inversely proportional to the cross-sectional area of the conductor. 

Electrical resistance monitors use the fact that the resistance of a conductor varies inversely as its cross-sectional area. In principle, then, a wire or strip of the metal of interest is exposed to the corrodent and its resistance is measured at regular intervals. In practice, since the resistance also varies with temperature, the resistance of the exposed element is compared in a Wheatstone bridge circuit to that of a similar element which is protected from the corrodent but which experiences the same temperature. 

In the above relationship p is an intrinsic property called the specific resistance (or resistivity) of the conductor. The definition of the specific resistance of any given conductor follows from this relationship. It is the resistance in ohms of a specimen of the material, 1 cm long and 1 cm2 in cross-sectional area (units ohm cm-1), the length being in the direction of the current and the cross-section normal to it. In other words, the specific resistance p of a conductor is the resistance of a cube of 1 centimeter edge. If the conductance is denoted by C = 1 /R, then the specific conductance (or conductivity) K, is given by JC= 1/a (units ohm-1 cm-1, mho cm-1, reciprocal ohm cm-1). Therefore, the relationship R = aL/A may be written as R = L/KA (units ohms) and the conductance can be expressed as C = 1/R = KA/l (units reciprocal ohms). 

The conductance of an electrolyte solution characterizes the easiness of electric conduction its unit is reciprocal ohm, = siemens = S = A/V. The electric conductivity is proportional to the cross-section area and inversely proportional to the length of the conductor. The unit of conductivity is S/m. The conductivity of an electrol3de solution depends on the concentration of the ions. Molar conductivity, denoted as X, is when the concentration of the hypothetical ideal solution is 1 M = 1000 mol/m. Hence, the unit of molar conductivity is either Sm M , or using SI units, Sm mol . For nonideal solutions, X depends on concentration, and the value of X at infinite dilution is denoted by subscript "0" (such as >,+ 0, and X for cation and anion molar conductivity). The conductivity is a directly measurable property. The molar conductivity at infinite dilution may be related to the mobility as follows ... 

The thermal effects caused by short-circuits can be calculated as follows the overtemperature AT of a conductor of length l, resistance R, cross-sectional area A and volume V, made of material with density cr and mass m, specific heat c and specific resistance p, caused by the current /(t), and without any heat dissipation to the environment, reads ... 

For a cylindrical conductor with length / and radius r, the cross-sectional area is irr2 and the total volume V = nr2 /. The surface S is 2-rrrl, and so the ratio S/V follows with 2/r. Diameters from 0.035mm to 0.5mm, i.e. a ratio 0.07 1, will be loaded with inverse current density ratios, in this example 16,17, corresponding to 1 0.062. 

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