In this blog, we will testimonial the principle of resistance, resistivity and steps to calculation the minimum cross-sectional area and diameter of any kind of desired conductor.

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What is Resistance?

The home of a an equipment or a circuit that opposes the movement of existing through it. Resistance is measure up in Ohms (Ω). The resistance of any kind of material through a uniform cross-sectional area is established by the following four factors:

The sort of materialThe lengthThe cross-sectional areaThe temperature

What is Resistivity?

Resistivity is the measure up of exactly how much a offered size of certain material resists the present flow. While materials resist electrical present flow, part are better at conducting it 보다 others. Resistivity is offered to compare the innate resistance features of different materials. Products that quickly conduct existing are referred to as conductors. Conductors have actually a low resistivity. While the products that carry out not quickly conduct current are described as insulators. Insulators have a high resistivity. The resistivity of a product plays crucial role in picking the products used for electric wire.

Now the we recognize the ide of resistance and also resistivity clearly, let’s testimonial the basic relationship of an easy conductor resistance, which argues that the resistance that a given conductor is same to the product resistivity time the proportion of its size to its cross-sectional area. This can help us to calculation the minimum cross-sectional area and also diameter of any type of desired conductor.

Let’s work out an instance to recognize the actions to calculation the minimum cross-sectional area and diameter of any kind of desired conductor.

Example: What is the minimum cross-sectional area and diameter the conductor because that a 750-meter-long copper wire having actually a preferably resistance that 0.2 ohms?

Minimum Cross-sectional Area:

To deal with this problem, us will usage the basic relationship because that calculating conductor resistance using the formula below:

Resistance = Resistivity * (Length / Area )


R =


R = Resistance of material, in Ohms

Ρ = product Resistivity, in Ohms per meter

L = Conductor Length, in meters

A = Cross-sectional Area, in square meters

In order to use this basic relationship to settle our instance problem, we require the specific resistance or resistivity of copper. Keep in mind that we obtain the resistivity of conductor products from the table that conductor resistivity and we understand now that copper has a resistivity of 1.72 x 10e-8 ohms every meter.

While resolving Conductor Resistance, remember come express resistance in ohms, product resistivity in ohms per meter, conductor length in meters, and cross-sectional area in square meters because that this connection to be valid. We can then move on to calculation the cross-sectional area that the cable by substituting because that the recognized quantities in the example. 

A =

Eq. (1)




Diameter that the conductor:

Area the a circle can be represented using listed below formula. We will need to rearrange the formula to resolve for diameter.

A =


4*A =



d =


We deserve to now instead of our gained cross-sectional area worth from Eq. (1) into this relationship and also calculate the diameter the the copper wire to arrive at a diameter that 0.009062 meters.

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d = 4*0.00006453.1415920.5


d = (8.212395*10-5)0.5

d = 0.009062 m

Now that we have actually the systems values, us will transform them and also express our last answer using the conventional units. 

A = 0.0000645 m2 = 64.5 mm2

d = 0.009062 m = 9.062 mm

Thereby, us conclude the our copper cable must have actually a minimum cross-sectional area the no much less than 64.5 mm^2 and a diameter of no much less than 9.062 mm.