I know that the correct answer is the one with the X next to it but I do not und
ID: 1770144 • Letter: I
Question
I know that the correct answer is the one with the X next to it but I do not understand how the answer was determined. Thanks!
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A semicircular loop of radius R that lies flat on the paper carries a clockwise current I as shown in the figure to the right above. The loop is immersed in a uniform magnetic field of magnitude B that points into the paper B = B kˆ . Find the total magnetic force on the loop using iˆ, jˆ, kˆ notation.
[A] F = 2IRB iˆ
[X] F = 2IRB jˆ
[C] F = IRB kˆ
[D] F = 2IRB kˆ
[E] F = 2IRB kˆ
Explanation / Answer
We know that, magnetic force F = i L x B
L vector for this loop is a vector from left end to right end, So L = 2R i^
F = i * (2R i^) x (-B k^)
= 2iRB j
second option is correct.