Proračun provodnika interfona

Wire diameter d  unit  |  Cross-sectional area A  unit2    |          ↓  |        ↓    |     Cross-sectional area A  unit2  |  Wire diameter d  unit    |

The "unit" is usually millimeters but it can also be inches, feet, yards, meters (metres), or centimeters, when you take for the area the square of that measure.

The cross section or the cross sectional area is the area of such a cut. It need not necessarily have to be a circle.   Commercially available wire (cable) size as cross sectional area: 0.75 mm2, 1.5 mm2, 2.5 mm2, 4 mm2, 6 mm2, 10 mm2, 16 mm2.

Calculation of the cross sectionA, entering the diameter d = 2 r:

r = radius of the wire or cable d= 2 r = diameter of the wire or cable
Calculation of the diameter d = >2 r, entering the cross section A:
 

The conductor (electric cable)

There are four factors that affect the resistance of a conductor: 1) the cross sectional area of a conductor A, calculated from the diameter d 2) the length of the conductor 3) the temperature in the conductor 4) the material constituting the conductor

 

There is no exact formula for the minimum wire size from the maximum amperage. It depends on many circumstances, such as for example, if the calculation is for DC, AC or even for three-phase current, whether the cable is released freely, or is placed under the ground. Also, it depends on the ambient temperature, the allowable current density, and the allowable voltage drop, and whether solid or litz wire is present. And there is always the nice but unsatisfactory advice to use for security reasons a thicker and hence more expensive cable. Common questions are about the voltage drop on wires.

Voltage drop Δ V

The voltage drop formula with the specific resistance (resistivity)ρ (rho) is:      Δ V = I × R = I × (2 × l × ρ / A)      I = Current in ampere l = Wire (cable) length in meters (times 2, because there is always a return wire) ρ = rho, electrical resistivity (also known as specific electrical resistance or volume resistivity) of copper = 0.01724 ohm×mm2/m (also Ω×m) (Ohms for l = 1 m length and A = 1 mm2 cross section area of the wire)     ρ = 1 / σ A = Cross section area in mm2 σ = sigma, electrical conductivity (electrical conductance) of copper = 58 S·m/mm2

Quantity of resistance      R = resistance Ω  ρ = specific resistance   Ω×m   l = double length of the cable   m  A = cross section mm2

The derived SI unit of electrical resistivity ρ is Ω × m, shortened from the clear Ω × mm² / m.
The reciprocal of electrical resistivity is electrical conductivity.

Electrical conductivity and electrical resistivityκor σ= 1/ρ
Electrical conductance and electrical resistance ρ = 1/κ = 1/σ 

 

Electrical  conductor	Electrical conductivity  Electrical conductance	Electrical resistivity  Specific resistance
silver	σ = 62 S·m/mm²	ρ = 0.0161 Ohm∙mm²/m
copper	σ = 58 S·m/mm²	ρ = 0.0172 Ohm∙mm²/m
gold	σ = 41 S·m/mm²	ρ = 0.0244 Ohm∙mm²/m
aluminium	σ = 36 S·m/mm²	ρ = 0.0277 Ohm∙mm²/m
constantan	σ = 2.0 S·m/mm²	ρ = 0.5000 Ohm∙mm²/m

Difference between electrical resistivity and electrical conductivity

The conductance in siemens is the reciprocal of the resistance in ohms.

 

To use the calculator, simply enter a value. The calculator works in both directions of the↔ sign.

Electrical conductivity σ  S × m / mm²	↔	Specific elec. resistance ρ  Ohm × mm² / m
σ = 1 / ρ		ρ = 1 / σ
siemens S = 1/Ω or ohm Ω = 1/S

The value of the electrical conductivity (conductance) and the specific electrical resistance (resistivity) is a temperature dependent material constant. Mostly it is given at 20 or 25°C.

Resistance = resistivity x length / area

The specific resistivity of conductors changes with temperature. In a limited temperature range it is approximately linear: where α is the temperature coefficient,T is the temperature andT0 is any temperature, such as T0 = 293.15 K = 20°C at which the electrical resistivity ρ (T0) is known.

Convert resistance to electrical conductance
Conversion of reciprocal siemens to ohms
1 ohm [Ω] = 1 / siemens [1/S]
1 siemens [S] = 1 / ohm [1/Ω]

To use the calculator, simply enter a value. The calculator works in both directions of the ↔sign.

Resistance R  ohms Ω	↔	Electrical conductance G  siemens S
R = 1 / G		G = 1 / R

1 millisiemens = 0.001 mho = 1000 ohms

Mathematically, conductance is the reciprocal, or inverse, of resistance: The symbol for conductance is the capital letter "G" and the unit is the mho, which is "ohm" spelled backwards. Later, the unit mho was replaced by the unit Siemens − abbreviated with the letter "S".

Calculator: Ohm's law

Table of typical loudspeaker cables

Cable diameter d	0.798 mm	0.977 mm	1.128 mm	1.382 mm	1.784 mm	2.257 mm	2.764 mm	3.568 mm
Cable nominal cross section A	0.5 mm2	0.75 mm2	1.0 mm2	1.5 mm2	2.5 mm2	4.0 mm2	6.0 mm2	10.0 mm2
Maximum electrical current	3 A	7.6 A	10.4 A	13.5 A	18.3 A	25 A	32 A	-

Always consider, the cross section must be made larger with higher power and higher length of
the cable, but also with lesser impedance. Here is a table to tell the possible power loss.

Cable length in m	Section    in mm2	Resistance in ohm	Power loss at		Damping factor at
			Impedance 8 ohm	Impedance 4 ohm	Impedance 8 ohm	Impedance 4 ohm
1	0.75	0.042	0.53%	1.05%	98	49
	1.50	0.021	0.31%	0.63%	123	62
	2.50	0.013	0.16%	0.33%	151	75
	4.00	0.008	0.10%	0.20%	167	83
2	0.75	0.084	1.06%	2.10%	65	33
	1.50	0.042	0.62%	1.26%	85	43
	2.50	0.026	0.32%	0.66%	113	56
	4.00	0.016	0.20%	0.40%	133	66
5	0.75	0.210	2.63%	5.25%	32	16
	1.50	0.125	1.56%	3.13%	48	24
	2.50	0.065	0.81%	1.63%	76	38
	4.00	0.040	0.50%	1.00%	100	50
10	0.75	0.420	5.25%	10.50%	17	9
	1.50	0.250	3.13%	6.25%	28	14
	2.50	0.130	1.63%	3.25%	47	24
	4.00	0.080	1.00%	2.00%	67	33
20	0.75	0.840	10.50%	21.00%	9	5
	1.50	0.500	6.25%	12.50%	15	7
	2.50	0.260	3.25%	6.50%	27	13
	4.00	0.160	2.00%	4.00%	40	20

The damping factor values show, what remains of an accepted damping factor of 200
depending on the cable length, the cross section, and the impedance of the loudspeaker.
Conversion and calculation of cable diameter to AWG
and AWG to cable diameter in mm - American Wire Gauge

Wire diameter d  mm   |  AWG number       |          ↓  |        ↓    |    AWG number     |   Wire diameter d  mm     |

The gauges we most commonly use are even numbers, such as 18, 16, 14, etc. If you get an answer that is odd, such as 17, 19, etc., use the next lower even number.   AWG stands for American Wire Gauge and refers to the strength of wires. These AWG numbers show the diameter and accordingly the cross section as a code. They are only used in the USA. Sometimes you find AWG numbers also in catalogues and technical data in Europe.

American Wire Gauge - AWG Chart

AWG number	46	45	44	43	42	41	40	39	38	37	36	35	34
Diameter in inch	0.0016	0.0018	0.0020	0.0022	0.0024	0.0027	0.0031	0.0035	0.0040	0.0045	0.0050	0.0056	0.0063
Diameter (Ø) in mm	0.04	0.05	0.05	0.06	0.06	0.07	0.08	0.09	0.10	0.11	0.13	0.14	0.16
Cross section in mm2	0.0013	0.0016	0.0020	0.0025	0.0029	0.0037	0.0049	0.0062	0.0081	0.010	0.013	0.016	0.020
AWG number	33	32	31	30	29	28	27	26	25	24	23	22	21
Diameter in inch	0.0071	0.0079	0.0089	0.0100	0.0113	0.0126	0.0142	0.0159	0.0179	0.0201	0.0226	0.0253	0.0285
Diameter (Ø) in mm	0.18	0.20	0.23	0.25	0.29	0.32	0.36	0.40	0.45	0.51	0.57	0.64	0.72
Cross section in mm2	0.026	0.032	0.040	0.051	0.065	0.080	0.10	0.13	0.16	0.20	0.26	0.32	0.41
AWG number	20	19	18	17	16	15	14	13	12	11	10	9	8
Diameter in inch	0.0319	0.0359	0.0403	0.0453	0.0508	0.0571	0.0641	0.0719	0.0808	0.0907	0.1019	0.1144	0.1285
Diameter (Ø) in mm	0.81	0.91	1.02	1.15	1.29	1.45	1.63	1.83	2.05	2.30	2.59	2.91	3.26
Cross section in mm2	0.52	0.65	0.82	1.0	1.3	1.7	2.1	2.6	3.3	4.2	5.3	6.6	8.4
AWG number	7	6	5	4	3	2	1	0 (1/0) (0)	00 (2/0) (-1)	000 (3/0) (-2)	0000 (4/0) (-3)	00000 (5/0) (-4)	000000 (6/0) (-5)
Diameter in inch	0.1443	0.1620	0.1819	0.2043	0.2294	0.2576	0.2893	0.3249	0.3648	0.4096	0.4600	0.5165	0.5800
Diameter (Ø) in mm	3.67	4.11	4.62	5.19	5.83	6.54	7.35	8.25	9.27	10.40	11.68	13.13	14.73
Cross section in mm2	10.6	13.3	16.8	21.1	26.7	33.6	42.4	53.5	67.4	85.0	107.2	135.2	170.5