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CBSE Class 10 Answered

Area of cross section of a conductor is increased two times if its resistance is 20 ohm. Find the new resistance. 
Asked by agraharianiruddha | 28 Jun, 2018, 16:54: PM
answered-by-expert Expert Answer
Resistance R =  begin mathsize 12px style rho L over A end style   , where ρ is resistivity, L is length and A is area of cross section.
we have begin mathsize 12px style rho L over A end style = 20Ω.
if cross section area is doubled,then new resitance R' = begin mathsize 12px style rho fraction numerator L over denominator 2 A end fraction space equals space 1 half rho L over A space equals space 1 half cross times 20 space equals space 10 capital omega end style

it is assumed the cross section is doubled by keeping the length same.
Answered by Thiyagarajan K | 28 Jun, 2018, 21:22: PM

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