When a potential difference is applied across the ends of a uniform wire of length l and radius r, a current I flows in the wire. If same potential difference is applied to the ends of another wire of the same material but of length 2l and radius 2r, the current in the wire is:
Correct answer: B. 2I
- A. I/4
- B. 2I
- C. I
- D. I/2
Explanation
R=ρl/AWhen radius is doubled : Area=2*pi*(2r) = 2*pi*4rHence the area has increased by 4 times.New resistance : Rx = ρ*2l/4A = ½ RV=IR where V remains same and R becomes halfI = V / ½RI become equal to 2I.
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