Engineering
Physics
Magnetic Force on a Current Carrying Wire
Question

A conductor (shown in the figure) carrying constant current I is 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 statement(s) is (are)

If B is along x^, F = 0

If B is along z^, F  (L + R)

If B is along y^, F (L + R)

If B is along z^, F = 0

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Solution

In uniform B, random shaped conductor can also be replaced by a straight conductor of length

= L + 2R + L = 2(R + L) i^

(A) F=i×B = 2i (+ L) ( (i^  ×k^) B0= 2iB0 (+ L)(j^),         F (R + L)

(B) F=0  if B=B0i^  as =^ × B=0

(C) F=2i(R+L)  (i^×j^)B0 = 2iB0 + (R + L) k^,        F(R + L)

(D) F=2iB0(R+L)(i^×k^)0