Question

Q. A semicircular wire PQS of radius R is connected to a wire bent in the form of a sine curve to form a closed
loop as shown in the figure. If the loop carries a current and is placed in a uniform magnetic field B. then
the total force acting on the sine curve is

(1) 2BiR (downward)
2)2BiR(upward)
3)BiR(upward)
4)Zero
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Answer 1

Answer:

no magnetic force act on it but a force which makes the loop into a circle act upward(thumb rule) and that force is 2BIR