Magnetic fields and the right hand grip rule

AI Thread Summary
The magnetic field at point O, located 10 cm from a wire carrying a 1.0 A current directed into the page, has a magnitude of 2 µT and a downward direction, as calculated using the formula B(r) = μ i / 2π r and the right hand grip rule. For the second wire, also carrying a 1.0 A current, to create a non-zero magnetic field at point O, the current must flow out of the page; if it flows into the page, the fields would cancel each other out. The calculations and reasoning provided are confirmed to be correct. The right hand grip rule is essential for determining the direction of the magnetic field. Understanding these principles is crucial for solving similar problems in electromagnetism.
shyguy79
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Homework Statement


(i) Find the magnitude and direction of the magnetic field at the point O located at a distance D = 10 cm from a wire carrying a current i = 1.0 A directed into the page, as shown in the attached drawing.

(ii) A second wire, identical to the first, is placed a distance D = 10 cm on the opposite side of O from the first wire as shown in Figure 3. This second wire carries a current with the same magnitude of i = 1.0 A. In which direction must this current flow in order for the magnetic field strength at O to be non* zero?

Homework Equations


Right hand grip rule
B(r) = μ i / 2π r

The Attempt at a Solution


For (i) I've got the magnitude of the field as 2uT from the B(r) = u i / 2π r and the direction as downwards using the right hand grip rule.

For (ii) I'm assuming that for it to be non zero then the current would have to be directed out of the page - if it was into the page then the resultant would be zero?
 

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shyguy79 said:

Homework Statement


(i) Find the magnitude and direction of the magnetic field at the point O located at a distance D = 10 cm from a wire carrying a current i = 1.0 A directed into the page, as shown in the attached drawing.

(ii) A second wire, identical to the first, is placed a distance D = 10 cm on the opposite side of O from the first wire as shown in Figure 3. This second wire carries a current with the same magnitude of i = 1.0 A. In which direction must this current flow in order for the magnetic field strength at O to be non* zero?

Homework Equations


Right hand grip rule
B(r) = u i / 2π r

The Attempt at a Solution


For (i) I've got the magnitude of the field as 2uT from the B(r) = u i / 2π r and the direction as downwards using the right hand grip rule.

For (ii) I'm assuming that for it to be non zero then the current would have to be directed out of the page - if it was into the page then the resultant would be zero?
attachment.php?attachmentid=43816&d=1329071935.jpg


(i) I didn't check the numbers, but that's the way to calculate the B-field at point O

For (ii), You have the correct result, but it's not so much an assumption as it is a well-reasoned conclusion.
 
Thank you SammyS (i) that's exactly what the question asked for and (ii) I thought so... cheers - I feel so much better now.
 
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