. A copper wire has diameter 0.5 mm and resistivity of
1.6 x 10-8 m. What will be the length of this wire to make its resistance 10 ? How much does the resistance change if the diameter is doubled
Answer: (a) From the given information
Thus, the length of copper wire required to make 10 resistance will be 122.5 meters.
(b) The resistance of a wire is inversely proportional to the square of its diameter. So, when the diameter of the wire is doubled (that is, made 2 times), then its resistance will become (one-fourth).