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प्रश्न
If the length of a wire is doubled by taking more of wire, what happens to its resistance?
उत्तर
We know that the resistance of the wire, R = ρl / A where the resistivity of the wire is ρ.
The length of the wire = l
The area of cross-section of the wire, A = πr2
The area of cross-section of the wire, A = πr2
So when the length of the wire is doubled (l' = 2l) by taking more of the same wire, (it will keep the resistivity and the area of cross-section the same), the length is doubled.
New resistance = R'
R' = ρl' / A
R' = 2ρl / A
R' = 2R
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