Final answer:
To balance the gravitational force acting on the wire, the minimum magnetic-field strength needed is approximately 0.180 T.
Step-by-step explanation:
The gravitational force acting on the wire can be calculated using the formula:
Fg = mg
where Fg is the gravitational force, m is the mass of the wire, and g is the acceleration due to gravity.
The magnetic force acting on the wire can be calculated using the formula:
Fm = BIL
where Fm is the magnetic force, B is the magnetic field strength, I is the current in the wire, and L is the length of the wire.
In order to balance the gravitational force, the magnetic force must be equal in magnitude. Therefore, we can set Fg = Fm and solve for B:
B = mg / (IL)
Substituting the given values into the formula, we get:
B = (0.045 kg * 9.8 m/s^2) / (11.0 A * 0.22 m)
Solving this equation yields a magnetic field strength of approximately 0.180 T.