Two conductors are made of the same material and have the same length. Conductor A is a solid wire of diameter 2.4 mm. Conductor B is a hollow tube of outside diameter 8.0 mm and inside diameter 4.0 mm. What is the resistance ratio RA/RB, measured between their ends?

                  =

Explanation:

For the two conductors A and B, the required general formula is;

                        R = ρl ÷ A

But since the two conductors are made of the same material,

                        ρA = ρB

Also, they have the same length,

                          lA = lB

So that,

                          =

Area can be calculated by .

Conductor A has diameter 2.4mm, thus its radius is 1.2mm. Conductor B has outside diameter 8.0mm of radius 4.0 and inside diameter 4.0mm of radius 2.0mm. Thus,

       =

By appropriate divisions,

       =

           =

      =

The resistance ratio measured between their ends is .

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