Question

if wireof length is increased twise from previous length and breadth decreased to half . what is the ratio of R' and R​

Answer 1

HEY!!

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⚫Resistance ‘R’ is related to length ‘L’, area of cross-section ‘A’ and resistivity ‘ρ’ as,

⚫R = ρL/A

⚫When the length of the wire is doubled its area of cross-section should change in such a way that the volume of the wire remains constant.

⚫Volume = A×L = A/×2L => A/ = A/2

⚫So, the new resistance is,

⚫R / = ρ(2L)/(A/2) = 4 ρL/A

=> R / = 4R

⚫Since, R = 20 Ω

R/ = 80 Ω