Hall pressure sensors are made based on the Hall effect of certain semiconductor materials. The Hall effect is the phenomenon that when a solid conductor is placed within a magnetic field and a current is passed through it, the charge carriers within the conductor are deflected to one side by the Lorentz force, which then generates a voltage (Hall voltage). The electric field force induced by the voltage balances the Lorentz force. The polarity of the Hall voltage confirms that the current inside the conductor is caused by the movement of negatively charged particles (free electrons).