Understand the area of its cross section as **the section** of a wire. She can be recognized directly upon purchase of a wire. If it did not work well, measure diameter of a wire by a caliper and count the cross-sectional area as the area of a circle. Also cross-sectional area can be found by means of the ampermeter, the voltmeter and a ruler.

## It is required to you

- caliper, ruler, ampermeter, voltmeter and table of specific resistance of substances.

## Instruction

1. Determination of section geometrical metodamipodavlyayushchy most of conductors has round shape of cross section. For its definition determine diameter of a wire in millimeters by a caliper, previously having removed from it if necessary isolation. Square diameter increase by 3.14, divide result into 4 (S=D²\• 3.14/4). Receive wire section in mm². In case the wire has rectangular section, measure by a caliper length and width of section in meters and multiply their values. Measure more irregular shapes of sections by other methods.

2. Determination of section of a wire in an electric tsepiprisoyedinita the conductor to a current source, turn on the ampermeter in a chain, and attach the voltmeter to the ends of the conductor. If the source gives a direct current, surely consider polarity at connection of devices. The positive pole of the device has to adjoin a positive pole of a source. For alternating current the polarity does not matter. After that close a chain and take readings from the ampermeter and the voltmeter, respectively, in amperes and volts. Define material of which the wire is made and determine the specific resistance of a wire in Ohm by the table of specific resistance of materials • mm²/м.

3. Measure by a ruler its length and transfer it to meters. Multiply values of specific resistance of material of the conductor, its length and force of the current proceeding on the conductor. Divide the received value into tension measured on the conductor (S=ρ\• l • I/U). Wire cross-sectional area in mm² will be result. To receive result in m², it is necessary to increase the received number by 10^(-6).