Physics: motional emf

Notice that the question asks for the induced emf ACROSS the wingtips, i.e. the potential difference between the left and right tips of the wings.

If we resolve the direction of B (magnetic flux density) into vertical and horizontal components, the vertical component is B.sin(theta) and horizontal component is B.cos(theta).

Now, because the speed of the aircraft is pointing out of the paper, the vertical component of B will produce an induced emf, by Fleming's Right Hand Rule, on the wingtips, with the left hand side higher in potnetial than the right hand side. The magnitude of the induced emf is given by [B.sin(theta)]xv = Bxv.sin(theta)

The horizontal component of B will produce an induced emf between the top and bottom of the wings, which is not wha tis asked by the question.

Therefore, the correct answer should be Bxv.sin(theta). No option is correct.

[Your proposed answer Blv.sin(theta) only gives the induced emf across the body of the aircraft, not that of the wingtips.]