a wire of resistance 3 ohm resistance and 10 cm length is streched to 30 cm . Assuming that it has a uniform cross section , what will be its new resistance
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let new resis. = r'
let length = L
let cross section = A
let new length = L'
let new cross section = A'
Given : r = 3ohms
L = 10 cm
L' = 30cm
A = A'
sol. : p = rA/L
p = r'A'/L'
r/L = r'/L'
3/10 = r'/30
(3 × 30)/10 = r'
90/10 = r'
9 = r'
let length = L
let cross section = A
let new length = L'
let new cross section = A'
Given : r = 3ohms
L = 10 cm
L' = 30cm
A = A'
sol. : p = rA/L
p = r'A'/L'
r/L = r'/L'
3/10 = r'/30
(3 × 30)/10 = r'
90/10 = r'
9 = r'
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