Question
Physics Question on Current electricity
A wire of length l and resistance R is stretched to get the radius of cross-section 2r . Then the new value of R is
A
16 R
B
4 R
C
8 R
D
5 R
Answer
16 R
Explanation
Solution
R=πr2ρl Since, V1=V2 ⇒ l′×π(2r)2=l×πr2 ⇒ 4l′=l or l′=4l ∴ R′=πr2ρ4l×4=16R