Find the resistance and resistivity if a wire is streched so that the lenght becomes 3/2 times of its original lenght if its original resistance iis 20 ohm.
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We have
R. = row l^2 d /m
as in second condition the wire is same so row and m and d remains constant.
So R IS DIRECTLY PRAPORTIONAL TO L ^2
And R2/R1= ( L2/L1)^2
R2/R1= (3L1/2L1)^2
R2=9/4 × R1
R2 = 9/4 ×20
R2 = 45 ohm
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