Question

How to accurately measure lorentz force?

Answer 1

If either the wire or the magnet is on a pendulum you could use displacement of the pendulum. For extra credit you move the top of the pendulum to get wire centered again - this takes out nonlinearity in the magnetic field. As long as the pendulum is long the force will be proportional to displacement and can be calculated very accurately (longer pendulum = potentially greater accuracy)

Answer 2

Answer:

Lorentz force, the force exerted on a charged particle q moving with velocity v through an electric field E and magnetic field B. The entire electromagnetic force F on the charged particle is called the Lorentz force (after the Dutch physicist Hendrik A. Lorentz) and is given by F = qE + qv × B.