Q.

One end of a horizontal thick copper wire of length 2L and radius 2R is welded to an end of another horizontal thin copper wire of length L and radius R. When the arrangement is stretched by applying forces at two ends, the ratio of the elongation in the thin wire to that in the thick wire is                      [2013]

1 0.25  
2 0.50  
3 2.00  
4 4.00  

Ans.

(3)

Using, Y=F/AΔ/0

Y=F/π(2R)2Δ1/2L=F/πR2Δ2/L

 Δ2Δ1=2