Loading....
Coupon Accepted Successfully!

 

Stretching of Wire

If a conducting wire stretches, its length increases, area of cross section decreases. So resistance increases but volume remains constant.
 
Suppose for a conducting wire before stretching (Fig. 11) its length = l1, area of cross section = A1, radius = r1, diameter = d1, and resistance 70583.png.
 
73406.png
Fig. 11
 
After stretching length = l2, area of cross section = A2, radius = r2, diameter = d2, and resistance 70590.png.
 
Ratio of resistances before and after stretching
 
70597.png
⇒ If length is given then 70603.png
⇒ If radius is given then 70609.png

 

Notes:
  • After stretching if length increases by n times, then resistance will increase by n2 times, i.e., R2 = n2R1. Similarly, if radius be reduced to 1/n times, then area of cross section decreases 1/n2 times. So the resistance becomes n4 times, i.e., R2 = n4R1.
  • After stretching, if length of a conductor increases by x%, then resistance will increases by 2x% (valid only if x < 10%).




Test Your Skills Now!
Take a Quiz now
Reviewer Name