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This problem is really driving me nuts.
A strip that runs up and down the page is placed in a magnetic field that is INTO the page. Current runs up the strip. The magnetic field creates a charge separation between the left and right-hand sides of the strip. There is a point a on the left side of the strip and a point b on the right side.
The question asks, Assume the charge carriers are electrons. What is true about the voltage between point a and point b?
Since the conventional current is running up the page, the electrons are running down the page. To calculate the force of the magnetic field on the electron, I therefore point my thumb UP (opposite the v of the electron). The force is therefore to the left of the page toward a.
Here's what trips me up. The direction of force on the electron and on the proton must be opposite. However, if I compute force on a positive charge moving in the direction of current up the page, I get a force ALSO toward the left.
What am I doing wrong?!
Edit: Thinking about this more thoroughly, it seems that a negative test charge moving down the page and a positive one moving up the page WOULD be directed toward the same direction, since their v and q are BOTH opposite. Thus, the charge separation on the strip is not caused by splitting the positive and negative charges, since there is no positive charge moving in the field, but just by forcing electrons to the left. It makes sense that if positive charge moved up and negative down, either way there would be a force to the left of a wire in this magnetic field.
A strip that runs up and down the page is placed in a magnetic field that is INTO the page. Current runs up the strip. The magnetic field creates a charge separation between the left and right-hand sides of the strip. There is a point a on the left side of the strip and a point b on the right side.
The question asks, Assume the charge carriers are electrons. What is true about the voltage between point a and point b?
Since the conventional current is running up the page, the electrons are running down the page. To calculate the force of the magnetic field on the electron, I therefore point my thumb UP (opposite the v of the electron). The force is therefore to the left of the page toward a.
Here's what trips me up. The direction of force on the electron and on the proton must be opposite. However, if I compute force on a positive charge moving in the direction of current up the page, I get a force ALSO toward the left.
What am I doing wrong?!
Edit: Thinking about this more thoroughly, it seems that a negative test charge moving down the page and a positive one moving up the page WOULD be directed toward the same direction, since their v and q are BOTH opposite. Thus, the charge separation on the strip is not caused by splitting the positive and negative charges, since there is no positive charge moving in the field, but just by forcing electrons to the left. It makes sense that if positive charge moved up and negative down, either way there would be a force to the left of a wire in this magnetic field.
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