Current Electricity 1 Question 12

12. In an aluminium (Al) bar of square cross section, a square hole is drilled and is filled with iron (Fe) as shown in the figure. The electrical resistivities of Al and Fe are 2.7×108Ωm and 1.0×107Ωm, respectively. The electrical resistance between the two faces P and Q of the composite bar is

(2015 Adv.)

(a) 247564μΩ

(b) 187564μΩ

(c) 187549μΩ

(d) 2475132μΩ

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Solution:

  1. 1R=1RAl+1RFe=AAlρAl+AFeρFe1

=(7222)2.7+2210106108×150×103

Solving we get,

R=187564×106Ω=187564μΩ



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