Wheatstone bridge principle is used to measure the specific resistance (S1) of given wire, having length L, radius r. If X is the resistance of wire, then specific resistance is ; S1=X ( r2L ). If the length of the wire gets doubled then the value of specific resistance will be :
- S14
- 2 S1
- S12
- S1
Answer
(4) S1
Solution
X= S1L r2; length doubled X'=2X
S1'=X' ( r22L )=2X ( r22L )=S1
Specific resistance (resistivity) depends only on the material and temperature, not on the length or thickness of the wire.
Answer: (4)