‌R1=100Ωl1=l ‌‌‌‌‌R2‌=?,l2=l1+20%‌ of ‌l1 ‌=l+0.2l=1.2l ∴‌‌R′‌=n2R=(1.2)2R ‌=1.44R=1.44×100=144Ω The wire of resistance 144Ω is bent into a rectangle with sides in the ratio 3:2. Let the side be 3x and 2x. Total length, l=2(3x+2x)=10x ∴‌‌R‌length ‌‌=‌
3x
10x
×144=43.2Ω R‌width ‌‌=‌
2x
10x
×144=28.8Ω The effective resistance across the diagonal is the equivalent resistance of two parallel branches. On branch consists of the other two sides of the same resistance. Each branch has a resistance of ‌R‌length ‌+R‌width ‌=43.2+28.8=72Ω ‌∴‌‌‌