Worked example: A 20 cm straight wire carries 5 A perpendicular to a uniform 0.4 T field. (a) Find the force. (b) If the wire is tilted to 30° from B, what is the force? (c) How much current would levitate a 10 g wire horizontally in this field? Step 1: (a) F = BIl = 0.4 × 5 × 0.2 = 0.4 N. Direction by Fleming's left hand, perpendicular to both. Step 2: (b) F = BIl·sin30° = 0.4 × 0.5 = 0.2 N. Step 3: (c) Magnetic force must balance weight: BIl = mg → I = mg/(Bl) = (0.01 × 9.8)/(0.4 × 0.2) = 0.098/0.08 = 1.225 A. This 'magnetic levitation' of a current loop is a classic demonstration — and the principle of maglev, scaled up with feedback control.