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Wonders of Physics


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Ratio of resistiviities of wires X and Y – effect of diameter on cross-sectional area

The resistance of two wires X and Y are in the ratio of 2 : 1, their lengths are in the ratio 1 : 2 and their diameters are also in the ratio of 1 : 2.

What is the ratio of the resistivities of wires X and Y?

A     1:2     B     1:1     C     2:1     D     4:1

Solutions: Option B

Note that when the diameter of the wire doubles, the cross-sectional area increases by 4 times.

Comparing the resistances of both X and Y as shown below, the ratio of resistivities is 1:1.

Notes page17

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