Question
Fri June 15, 2012 By:

A PIECE OF WIRE OF RESISTANCE 20OHM IS DRAWN SO THAT ITS LENGTH IS INCREASED TO TWICE ITS ORIGINAL LENGTH.CALCULATE RESISTANCE OF THE WIRE IN THE NEW SITUATION.

Expert Reply
Fri June 15, 2012
Let the initial cross-sectional area of the wire be a and after streching let it be A.
Let the initial length of the wire be l and hence the new length be L=2l
since after streching the volume of the wire will remain constant.
Initial volume:
Final volume:
Now
Since resistivity of the wire will remain constant thus, we can compare the old resistance with new as:
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