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1. Homework Statement
The figure is a cross section through three long wires with linear mass density 52.0g/m. They each carry equal currents in the directions shown. The lower two wires are 4.0 cm apart and are attached to a table. (please see attachment) Just in case attachment is not working (top wire is going out of page and above lower wires, which are going into the page.) What current will allow the upper wire to "float" so as to form an equilateral triangle with the lower wires?
View attachment 3 wires.doc
2. Homework Equations
F=uLI^2/(2pid)
F=mg
(please see attached for better format for equations)
ATTACH]13181[/ATTACH]
3. The Attempt at a Solution
since current in lower wires are in opposite direction from top wires, therefore they repel each other. The ycomponents from each lower two wires must equal force of gravity of top wire:
mg = 2 x uLI^2/(2pid)sin30
solve for I, assume L=1 m and where d=0.04m, mg=0.5096N
I=319A.....but why is this not the right answer?
The figure is a cross section through three long wires with linear mass density 52.0g/m. They each carry equal currents in the directions shown. The lower two wires are 4.0 cm apart and are attached to a table. (please see attachment) Just in case attachment is not working (top wire is going out of page and above lower wires, which are going into the page.) What current will allow the upper wire to "float" so as to form an equilateral triangle with the lower wires?
View attachment 3 wires.doc
2. Homework Equations
F=uLI^2/(2pid)
F=mg
(please see attached for better format for equations)
ATTACH]13181[/ATTACH]
3. The Attempt at a Solution
since current in lower wires are in opposite direction from top wires, therefore they repel each other. The ycomponents from each lower two wires must equal force of gravity of top wire:
mg = 2 x uLI^2/(2pid)sin30
solve for I, assume L=1 m and where d=0.04m, mg=0.5096N
I=319A.....but why is this not the right answer?
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