A conductor of length
has a uniform cross section.
The radius of cross section varies linearly from to .The resistivity of the material is .
Find the resistance of the conductor across its ends in Ohms .
Details and Assumptions
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The resistance of the conductor across its ends is given by: R = ∫ 0 l π r 2 ρ d x
where x is the distance along the axis from the left end and r is the radius of the cross section at x , and r = a + l b − a x = 0 . 0 2 + 0 . 3 x
Therefore,
R = ∫ 0 l π r 2 ρ d x = π ρ ∫ 0 l ( 0 . 0 2 + 0 . 3 x ) 2 d x
= 0 . 3 π ρ [ 0 . 0 2 + 0 . 3 x − 1 ] 0 l = 0 . 3 × 3 . 1 4 1 6 6 . 2 8 × 1 0 − 8 [ 0 . 0 2 1 − 0 . 0 5 1 ]
= 0 . 3 × 3 . 1 4 1 6 6 . 2 8 × 1 0 − 8 × 3 0 = 2 × 1 0 − 6 Ω