Angle between B-Field and X-axis

  • Thread starter hanagasumi
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  • #1
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Homework Statement



Two long horizontal straight parallel wires are 3.18 cm apart and each carries a current of 9.25 A in the directions shown in the above figure. What is the magnitude of the B-field at point P, which is at a perpendicular distance of 2.25 cm from both wires?


Homework Equations



What is the direction of the B-field at point P? Give the angle between the x-axis and the B-field in degrees (give your answer as an angle between 0 and 359 deg.).



The Attempt at a Solution



I did part 1, and found the magnitude of the B-field, which is 1.16×10-4 T and is correct, and then I'm stuck on part B, I think according to my image, the x and y components both will double, but it shouldn't affect my angle, but it's wrong. I think my assumption is wrong. Can anyone please help me with the angle?




Thank you very much!
 

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Answers and Replies

  • #2
supratim1
Gold Member
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the y components will cancel out, and the x components will add up. check it by thinking about the tangent to the magnetic field line at P due to each wire.
 
  • #3
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the y components will cancel out, and the x components will add up. check it by thinking about the tangent to the magnetic field line at P due to each wire.

If my y components cancel out and my x-components add up, then will my angle be 359?
 
  • #4
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How did you get the magnetic field in part 1?
 
  • #5
gneill
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How did you get the magnetic field in part 1?

What's the magnetic field strength at some distance r from a long, current carrying wire? What's its direction?
 
  • #6
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I'm stuck on a similar question as well.

My y components cancelled out and the total magnetic field is just 2*the x component of one wire.

Doesn't this mean it has to be in x direction if there's no y component..

It should be 180, but that's wrong and so is 0.

Actually, it's the x components that cancel out, not y, so the angle should be 270?
 
Last edited:
  • #7
gneill
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I'm stuck on a similar question as well.

My y components cancelled out and the total magnetic field is just 2*the x component of one wire.

Doesn't this mean it has to be in x direction if there's no y component..

It should be 180, but that's wrong and so is 0.

Is your question exactly the same or only similar? Current directions matter.
 
  • #8
86
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It's slightly different. Currents are in opposite directions. 270 doesn't seem to be correct either though.
 
  • #9
gneill
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It's slightly different. Currents are in opposite directions. 270 doesn't seem to be correct either though.

Well there you go; you'll need to see how that affects the B-field directions.
 

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