1. The problem statement, all variables and given/known data An aeroplane in horizontal flight has a wing span of 50 m and is travelling due north at a speed of 500 kmph. Calculate the emf induced between the wing tips of the aeroplane. The value of the vertical component of the Earth’s magnetic field is 5.5 x 10-5 T. What additional information would be needed to determine whether the left wing tip was positive or negative? 2. Relevant equations ε = BvL 3. The attempt at a solution 500 kmph = 500,000/3600 = 138.89 ms-1 ε = 5.5 x 10-5 T x 50m x 138.89 ms-1 ε = 0.38194V I hope thats right? lol Anyways I'm confused about the second part 'What additional information would be needed to determine whether the left wing tip was positive or negative?'