# Homework Help: Problem already solved. concept help needed. Four Wires in a square.

1. May 15, 2012

### runphysicsrun

Four Wires form corners of a square. Force exerted by 3 of them on 1. Concept help!

1. The problem statement, all variables and given/known data

side length "a"= 5.5 cm
current through wires "I" = 1.6A
"L" of lower right wire= 1 cm
upper and lower left currents are out of the page
upper and lower right currents are into the page

Problem Attached

My issue is with part b!

2. Relevant equations

F=ILB
B=μ0I /2∏R
Vector diagrams based on right hand thumb rule

3. The attempt at a solution

I've solved both parts of this problem. I solved the second part by creating vector diagrams and then applying Fx=ILB for the B's produced by the upper right and lower left wires. The lower left wire has a y-component as well so I multiplied by the cos (45). However, I'm having trouble comprehending why you can assume that the angle of the field vector by the lower left hand wire is exactly 45 degrees. Can anyone explain that to me?

Also appreciated would be if someone could draw the vector representations for part B (the forces of B acting on the wires), as I want to check my diagrams!

I have a cumulative exam next Monday, so help would be much appreciated!
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

#### Attached Files:

• ###### four wires.png
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Last edited: May 15, 2012
2. May 15, 2012