Data: m = 20 g = 2 × 10-2 kg, l = 1 m, I = 1 A,
g = 9.8 m/s2
To balance the wire, the upward magnetic force must be equal in magnitude to the downward force due to gravity.
∴ Fm = IlB = mg
Therefore, the magnitude of the magnetic field,
B = = 0.196 T