Class 4 (4th Engineer) MET 📅 Oct 2023

Exam Question

Ten thousand cubic millimetres of copper are (a) drawn into a wire 100 metres long, (b) rolled into a square sheet of 100mm side. Find the resistance of the wire and the resistance between opposite faces of the plate, if the resistance of the copper is 17 µΩmm or 1.7 x 10^-8 ohm-metres.

Reference Answer

### Objective
To calculate the electrical resistance of a given volume of copper when formed into two different shapes: a long wire and a thin square plate. The solution requires the application of the fundamental resistance formula, paying close attention to the geometric interpretation of length and cross-sectional area for each case.
### Governing Principle
The electrical resistance (R) of a uniform conductor is directly proportional to its length (l) and its resistivity (ρ), and inversely proportional to its cross-sectional area (A). The formula is:

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