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1)

 A conductor (shown in the figure) carrying constant current I in kept in the x-y plane in a uniform magnetic field B. If F is the magnitude of the total magnetic force acting on the conductor, then the correct statements is /are

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A) if B is along ˆz,F(L+R)

B) if B is along ˆx,F=0

C) If B is along ˆy,F(L+R)

D) if B is along ˆz,F=0

Answer:

Option A,B,C

Explanation:

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Force on the complete wire = force on straight wire PQ carrying a current I.

    F=I(PQ×B)

              =I[{2(L+R)ˆi}×B]

This force is zero if B  is along  ˆi  direction or x-direction . If magnetic  field is along ˆj  direction or ˆk  direction,

                  |F|=F=(I)(2)(L+R)Bsin900

         or              F= 2I(L+R)B

 or            F(L+R)

      Options (a),(b) and (c) are correct.