A wire has a resistance R. Find new resistance, (i) if radius of cross-section of a cylindrical wire is doubled, then find ratio of initial to final resistance. (ii) if length of wire is increased by `10%`, then find the percentage increase in its resistance. (iii) if length of wire is increased by `20%`, then find the percentage increase in its resistance. A. 0.1B. 0.2C. 0.4D. 0.21

A wire has a resistance R. Find new resistance, (i) if radius of cross

1.	A wire has a resistance R. Find new resistance, (i) if radius of cross-section of a cylindrical wire is doubled, then find ratio of initial to final resistance. (ii) if length of wire is increased by `10%`, then find the percentage increase in its resistance. (iii) if length of wire is increased by `20%`, then find the percentage increase in its resistance. A. 0.1B. 0.2C. 0.4D. 0.21
Answer» Correct Answer - D `l_(2)=1.1 l_(1),R_(2)-R_(1)=?` `(R_(2))/(R_(1))=((l_(2))/(l_(1)))^(2)` `R_(2)=((1.1 l_(1))/(l_(1)))^(2)xxR_(1)=1.21R_(1)` Now increase in resistance `=R_(2)-R_(1)` and % increase in resistance `=((R_(2)-R_(1))/(R_(1)))xx100` `=((1.21R_(1)-R_(1))/(R_(1)))xx100` `=21%`

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