In theory, the diameter of the conductors the cross-section of a cable correspond to the declared parameters. For example, if the marking indicates that the cable is 3 x 2.5, then the cross-section of the conductors should be exactly 2.5 mm2. In practice, it turns out that the actual size may differ by 20-30%, and sometimes even more. What does this threaten? Overheating or melting of the insulation with all the ensuing consequences. Therefore, before buying, it is advisable to know the size of the wire to determine its cross-section. How exactly to calculate the cross-section of the wire by diameter is what we will find out further.
How and what to measure the diameter of a wire
A caliper or any type of micrometer (mechanical or electronic) will do to measure the diameter of the wire. Electronic ones are easier to work with, but not dentist data has them. You need to measure the core itself without insulation, so first move it aside or remove a small piece. This can be done if the seller allows it. If not, buy a small piece for testing and take measurements on it. Measure the diameter on the conductor stripped of insulation, after how to choose a gaming smartphone you can determine the actual cross-section of the wire based on the dimensions found.
Measuring wire diameter with a micrometer is more accurate than with a mechanical caliper.
Which measuring device is better in this case? If we talk philippines numbers mechanical models, then a micrometer. It has higher measurement accuracy. If we talk about electronic options, then for our purposes they both give quite reliable results.
If you don’t have a caliper or a micrometer, take a screwdriver and a ruler with you. You’ll have to strip a pretty decent piece of wire, so you’ll probably need to buy a test sample this time. So, strip the insulation off a 5-10 cm piece of wire. Wind the wire onto the cylindrical part of the screwdriver. Place the turns tightly next to each other, without a gap. All the turns should be full, that is, the “tails” of the wire should stick out in one direction – up or down, for example.
Determining the diameter of a wire using a ruler
The number of turns is not important – about 10. It can be more or less, it’s just easier to divide by 10. You count the turns, then apply the the cross-section of a cable winding to the ruler, aligning the beginning of the first turn with the zero mark (as in the photo). Measure the length of the section occupied by the wire, then divide it by the number of turns. You get the diameter of the wire. It’s that simple.
For example, let’s calculate the size of the wire shown in the photo above. The number of turns in this case is 11, they occupy 7.5 mm. Divide 7.5 by 11, we get 0.68 mm. This will be the diameter of this wire. Then you can look for the cross-section of this conductor.
We are looking for the cross-section of the wire by diameter: formula
The wires in the cable have a circular cross-section. Therefore, when calculating, we use the formula for the area of a circle. It can be found using the radius (half the measured diameter) or the diameter (see the formula).
We determine the cross-section of the How to the cross-section of a cable by diameter: formula
For example, let’s calculate the cross-sectional area of a conductor (wire) based on the size calculated earlier: 0.68 mm. Let’s first use the formula with the radius. First, find the radius: divide the diameter by two. 0.68 mm / 2 = 0.34 mm. Then substitute this figure into the formula
S = π * R2 = 3.14 * 0.342 = 0.36 mm2
You need to calculate it like this: first, square 0.34, then multiply the resulting value by 3.14. We get the cross-section of this wire of 0.36 square millimeters. This is a very thin wire, which is not used in power networks.
Let’s calculate the cable cross-section by diameter using the second part of the formula. It should be exactly the same value. The difference may be in thousandths due to different rounding.
S = π/4 * D2 = 3.14/4 * 0.682 = 0.785 * 0.4624 = 0.36 mm2
In this case, we divide the number 3.14 by four, then square the diameter, and multiply the two resulting numbers. We get the same value, as it should be. Now you know how to find out the cross-section of a cable by diameter. Use How to the cross-section of a cable of these formulas is more convenient for you. There is no difference.
Table of correspondence of wire diameters and their cross-sectional area
It is not always desirable or possible to make calculations in a store or at a market. In order not to waste time on calculations or not to make a mistake, you can use a table of correspondence of diameters and cross-sections of wires, which contains the most common (standard) sizes. You can rewrite it, print it out and take it with you.
How to work with this table? As a rule, cables have markings or tags indicating their parameters. They indicate the cable marking, the How to the cross-section of a cable of cores and their cross-section. For example, VVNG 2×4. We are interested in the core parameters, which are the numbers that come after the “x” sign. In this case, it is stated that there are two conductors with a cross-section of 4 mm2. So we will check whether this information is true.