Saturday, September 21, 2019

homework and exercises - Confused with Right Hand Rule. Finding the direction of Force on wire segment due to magnetic field?


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First of all, this is not a HW question, and I know the answer.


I know I can find the direction of F which is F = IL x B


So I tried to put my index finger (I) pointing to right, and middle finger (B) pointing downward. This makes my thumb to point Into the Page. But the answer is actually the D direction. How does this work?


Also, the magnitude of the force is 61.9 N, but I am also confused of getting this answer using F = IL x B. Please help!



Answer



There are several ways to do the right hand rule. Yours does not work.


Try this one and see if it makes sense for you: form a right-angled triad with your thumb and first two fingers. $\vec{c}=\vec{a}\times \vec{b}$. First finger: $\vec{a}$. Second finger: $\vec{b}$. Thumb: the resultant, $\vec{c}$


In your example, first finger into the page, second finger down, thumb points in the $D$ direction.


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