Find a point where this magnetic field is zero

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Homework Help Overview

The discussion revolves around problems related to magnetic fields and forces involving current-carrying wires. The original poster presents multiple questions, including finding a current that results in a specific magnetic force, comparing torques of different coil shapes, and determining a point where the net magnetic field is zero between two parallel wires carrying currents in opposite directions.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the formula for the force on a current-carrying wire and the implications of the direction of currents in the context of magnetic fields. There are questions about whether the second and third problems involve ratios without numerical values. Some participants express uncertainty about the second question and seek clarification on the approach.

Discussion Status

Some guidance has been offered regarding the first question, specifically the formula for the force on a current-carrying wire. However, there is still uncertainty regarding the second question, and participants are exploring the nature of the problems without reaching a consensus on the methods to solve them.

Contextual Notes

The original poster indicates a lack of familiarity with the problems and seeks foundational formulas or approaches. There is an implication of homework constraints, as the questions are part of a recent assignment that the poster did not attempt due to confusion.

ShadowFX
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Two insulated wires, each 2.4 m long are taped together to form a two wire unit that is 2.4 m long. One wire carries a current of 7.00 A; the other carries a smaller current I in the opposite direction. The two wire unit is placed at an angle of 65.0 degrees relative to a magnetic field whose magnitude is 0.360 T. The magnitude of the net magnetic force experience by the two wire unit is 3.13 N. What is the current I?

A square coil and a rectangular coil are each made from the same length of wire. Each contains a single turn. The long sides of the rectangle are twice as long as the short sides. Find the ratio of torque of the square over the torque of the rectangle of the maximum torques that these coils experience in the same magnetic field when they contain the same current

Two long, straight parallel wires are separated by a distance of one meter. They carry currents in opposite directions, and the current in wire A is one-third of that in wire B. On a line drawn perpendicular to the wires, find the point where the net magnetic field is zero. Determine this point relative to wire A.

I have no clue at all how to do these questions or what unit they're from, I'm doing some studying and reviewing and these were on our last assignment but i didnt do them because i didnt know how... can someone give me some forumlas or something i could use to approach it?
 
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First question: the force on a current-carrying is F = LIxB, where L is the length of the wire, I is the current it carries, and B is the magnetic field. Note that you are taking the cross product of the I and B (in this order), so the direction of I has meaning. Also, two current-carrying wires exert force on each other (because each is creating a magnetic field around itself, and by that causing the other wire to experience a force), but in this case the two wires are considered one unit, so the internal forces can be ignored (I think, but I may be wrong).
 
thnx F=ILxB makes good sense.

now for the other two.. for the second and third one, they're just ratios? no numbers?
 

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