How can the cross-sectional area of a wire be found?

Measure the diameter of the wore, with a micrometer or digital calipers. Do this in several places and orientations and find the mean. Then divide the diameter by 2 to get the radius. then the area of a circle is pi x r squared.

The cross-sectional area cannot be found directly. The cross-sectional area of a wire is a circle. Firstly, one would need to measure the diameter of a wire and, once found, use the formula for the area of the circle and insert the value of the diameter or radius into the formula.

It is not possible to masure the diameter with a ruler as the diameter of a wire is usually less than 1mm. The diameter can be measured using a micrometer screw gauge. The micrometer would be used to measure the diameter in 3 different places on the wire and the mean value of the diameter would then be calculated. This reduces the uncertainty in the measurement of the diameter.