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Why do Americans say ohms per circular mil foot when it's actually ohms circular mils per foot?
Wiki User
∙ 12y ago
A circular mil is a unit of cross sectional area. A foot is a unit of length. Combine the two, getting circular mils foot and you have a measure of the amount of material involved in a unit length of a certain gauge wire.
One interesting use of the amount of material is the resistance of the wire. It makes sense to say "ohms per circular mil foot", because that will tell you the resistance as a function of gauge and length. This is simply a combination of ohms per circular mil and ohms per foot. This basically says that resistance is inversely proportional to cross sectional area, and proportional to length.
Ohms circular mils per foot sounds like its answering a totally different question about the conductor. I don't know what that usage might be.
CommentWe are talking about the US customary unit for resistivity, equivalent to the ohm metre in the SI system.Since the resistivity of a material is given by (RA)/l, dimensional analysis indicates quite clearly that the US-customary unit should be [(ohm x circular mil)/foot] -that is, ohm circular-mil per foot. So, unless we chuck dimensional analysis out of the window, then 'ohms per circular mil foot' clearly isn't correct!
So it remains a mystery to me as to why that's how it is shown in most (but not all) US textbooks. (The SI unit for resistivity, based on dimensional analysis, is the ohm metre -not the ohm per metre). Comments by others would be appreciated!
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∙ 12y ago
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What is mcm wire?
MCM is another measure of wire gauge. It is somewhat confusing but it starts at around 40 gauge being the smallest wire up to the largest gauge of 1. from there you have oughts which is from 1 to 4 (1 ought, 2 ought etc) and then you have MCM which is circular mils. MCM can range from something as small as 250 mcm up to 2000 mcm.Another AnswerThe abbreviation, 'MCM', stands for 'thousand circular mils'. A 'circular mil' is a North-American method of measuring the cross-sectional area of a circular-section conductor (Europeans use square millimetres for conductors of anyshape).A 'circular mil' is obtained by squaring the diameter of a circular-section conductor, expressed in mils. A 'mil' is one-thousandth of an inch. As the constant, 'pi', isn't taken into account, it should be obvious that a circular mil is, therefore, a figure representing a cross-sectional area, rather than a true measure of that area.If necessary, in order to obtain a true cross-sectional area, circular mils can be converted into square mils.
How thick is 18 gauge vinyl?
Roughly 15.6 mils or 15.6 thousandths of an inch. Roughly, 1 gauge = .86 mils.
What is difference between galvanised and epoxy coated steel?
Epoxy-polyester powder coating is a hybrid of epoxy and polyester powder coating, and galvanised is coating thickness for steel bars and components is between 3 and 4 mils.
Trade sizes of electrical wires and cables?
The National Electrical Code (US) list trade sizes in Chapter 9, Table 8, Conductor Properties: AWG (American Wire Gauge) 18, 16, 14, 12, 10, 8, 6, 4, 3, 2, 1, 1/0, 2/0, 3/0, 4/0 and by kcmil (thousand circular mils) 250, 300, 350, 400, 500, 600, 700, 800, 900, 1000, 1250, 1750, and 2000For EuropeIn Europe, the cross-sectional area of conductors is measured in square millimetres (mm2).
What is the new resistance level of a wire if the length is changed from 200 yard to 200 feet the area is changed 60000 CM to 0.09 in2 and the original resistance was 950 m ohms?
200 yards to 200 feet is easy, just divide by three. 0.09 square inches means the new wire has about 1.9 times the cross-sectional area of the old one (assuming CM means circular mils). So that would reduce the resistance by a further factor of 1.9. All told, I'm getting somewhere in the vicinity of 166 "m ohms" (milliohms?). I did not understand .I'm talking Arabic
How do you calculate mils to circular mils?
1 circular mil = 1 mil x 1 mil a=d2 so if a wire has a diameter of 80 mils, it has an area of 6400 circular mils.
What is .000025 circular inches to circular mil?
.000025 circular inches = 25 circular mils
How do you convert circular mils to sq inches?
1 Circular mil = 0.7854 x 10-6 Square InchConveter:http://www.unitconversion.org/area/circular-mils-to-square-inchs-conversion.htmlInformation from:http://www.engineeringtoolbox.com/mil-circular-mil-area-d_817.html
How many mils in 1 foot?
305 mm is 1 foot
Circular mils for 12 awg solid wire?
True
What mcm wire?
MCM is another measure of wire gauge. It is somewhat confusing but it starts at around 40 gauge being the smallest wire up to the largest gauge of 1. from there you have oughts which is from 1 to 4 (1 ought, 2 ought etc) and then you have MCM which is circular mils. MCM can range from something as small as 250 mcm up to 2000 mcm.Another AnswerThe abbreviation, 'MCM', stands for 'thousand circular mils'. A 'circular mil' is a North-American method of measuring the cross-sectional area of a circular-section conductor (Europeans use square millimetres for conductors of anyshape).A 'circular mil' is obtained by squaring the diameter of a circular-section conductor, expressed in mils. A 'mil' is one-thousandth of an inch. As the constant, 'pi', isn't taken into account, it should be obvious that a circular mil is, therefore, a figure representing a cross-sectional area, rather than a true measure of that area.If necessary, in order to obtain a true cross-sectional area, circular mils can be converted into square mils.
What is mcm wire?
MCM is another measure of wire gauge. It is somewhat confusing but it starts at around 40 gauge being the smallest wire up to the largest gauge of 1. from there you have oughts which is from 1 to 4 (1 ought, 2 ought etc) and then you have MCM which is circular mils. MCM can range from something as small as 250 mcm up to 2000 mcm.Another AnswerThe abbreviation, 'MCM', stands for 'thousand circular mils'. A 'circular mil' is a North-American method of measuring the cross-sectional area of a circular-section conductor (Europeans use square millimetres for conductors of anyshape).A 'circular mil' is obtained by squaring the diameter of a circular-section conductor, expressed in mils. A 'mil' is one-thousandth of an inch. As the constant, 'pi', isn't taken into account, it should be obvious that a circular mil is, therefore, a figure representing a cross-sectional area, rather than a true measure of that area.If necessary, in order to obtain a true cross-sectional area, circular mils can be converted into square mils.
What unit of measurement is used for the cross- section area of wires?
square millimetres.AnswerIt depends where you live.In Britain and Europe, the standard measurement is the square millimetre (mm2)In North America, circular-sectioned conductors are measured in circular mils (CM) or multiples (e.g. MCM -thousand circular mils). A circular mil is derived from the diameter of the conductor, in mils (thousands of an inch) squared -so it isn't really a true unit of area (as the constant, pi, isn't used), but simply a number that represents an area.
A conductor thats described as a 750 mcm wire has an area of?
750,000 circular mils. A wire that is 1 mil (.001 inches) in diamter is defined to have an area of 1 circular mil. The area in circular mils = (diameter in mils) ^ 2. To convert this to area in square inches, multiply 750,000 * pi / 4,000,000 = 0.589 sq in.
What does 250kcmil AWG mean?
It is a wire size, the equivalent cross sectional area in thousands of circular mils. e.g. 500 MCM or kcmil = 500,000 circular mils. The circular mil is a unit of area used especially when denoting the cross-sectional size of a wire. It is the equivalent area of a circle whose diameter is 0.001 (10-3) inch. AWG stands for American Wire Guage.
Write a formula used to find circular mil area?
The ddiameter of No. 14 wire is 64 mils. What is its area in CM and in SM?
Is ft the smallest unit in the US unit?
No, there are 1000 mils in an inch and 12 inches in a foot.
