Question

1. A 2-wire d.c. distributor 500 m long is loaded uniformly at the rate of 0-4A/m. If the voltage drop in the distributor is not to exceed 5V, calculate the area of X-section of each conductor required when the distributor is fed at one end. Take resistivity of conductor material as 1.7 x 100 ??n. [3.4 cm.]

Answer 1

Given 2 - wire dc distributor length l = 500 m uniformly loaded at the rate i = 0.4 A/m maximum voltage drop v = 54 let r dc resistance per unit length ie r Ohm/m is uniformly distributed since we know that voltage drop in distribution line V = ir [lx - x^2/x] where x = distance from free end here at x = l V = 5V (given) substituting values 5 = 0.4 times r [l^2 - l^2/2] 5 = 0.4 times r l^2/2 5 = 0.4 times r times (500)^2/2 r = 5 times 2/0.4 times (500)^2 r = 1 times 10^-4 Ohm/m for 2 wire line effective resistance per unit length r' = r/2 r' = 1/2 times 10^-4 Ohm/m \r\n let A be area of cross section required Resistance R = delta l/A delta = Resistivity Resistance per unit length R/l = delta/A r' = delta/A A = delta/r' substituting delta = 1.7 times 10^-8 Ohm m r' = 1/2 times 10^-4

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