1.

A resistance wire has a resistance R. Half of this wire is stretched to double its length and half is twisted to double the thickness, then its new resistance becomes1.  65R/32 2.  45R/323. 35R/324.  15R/32

Answer»

Correct option  1.   65R/32

Explanation:

(I) Half length increased to doubled

New length = l

New area = A/2

R' = 2R ′

(II) Half length twisted to double the thickness

New length l /4

New area = 2A

R' =  1/8 R

New resistance

 2R + 1/8R = 17/8R 



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