Magnetic field and wire current

AI Thread Summary
A long, straight wire with a linear mass density of 45 g/m is suspended in a uniform magnetic field, with a 7.0 A current causing it to deflect at a 10-degree angle. To determine the strength of the magnetic field B, the relevant equation for the force on a current-carrying wire segment in a magnetic field, F = ILB, should be used. The discussion emphasizes the importance of drawing a free body diagram to balance the forces acting on the wire. The initial equation provided for B is deemed irrelevant for this scenario. The focus is on finding the correct approach to calculate the magnetic field strength.
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Homework Statement


A long, straight wire with linear mass density of 45g/m is suspended by threads, as shown in the figure . There is a uniform magnetic field pointing vertically downward. A 7.0A current in the wire experiences a horizontal magnetic force that deflects it to an equilibrium angle of 10 degree. What is the strength of the magnetic field B?



Homework Equations



B=(U_o I) / (2 *3.14 * r)


The Attempt at a Solution



I have U_0 given, I given. but can't find r.

How can find r to get B?
 

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The equation that you have quoted gives the magnetic field produced by a very long wire. It is not relevant here. What equation do you know that gives the force on a current-carrying wire segment in a magnetic field?
 
F=ILB maybe?
 
That's the right equation.
The next step is to draw a free body diagram and balance the forces.
 

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