# Explain how the Hall effect arises when a current-carrying conductor is placed in a magnetic field perpendicular to the current, and state what determines the polarity of the Hall voltage produced.

> IB DP Physics Higher Level (2023 syllabus) — D.2 Electric and magnetic fields · Explain · 4 marks

> A flat rectangular conductor carries a conventional current in the positive x-direction. A uniform magnetic field is applied in the positive z-direction (perpendicular to the face of the conductor).

## Mark scheme (4 marks)

1. The magnetic force (Lorentz force) acts on the moving charge carriers, deflecting them towards one face of the conductor.
2. Charge accumulates on that face, creating an electric field (Hall field) across the width of the conductor.
3. Equilibrium is reached when the electric force due to the Hall field exactly balances the magnetic force on the charge carriers, so no further deflection occurs.
4. The polarity of the Hall voltage depends on the sign of the charge carriers: positive carriers (conventional current direction) and negative carriers (electrons moving opposite to conventional current) accumulate on opposite faces, producing opposite polarities.

## Key terms

- [Hall effect](https://www.gradenine.co.uk/glossary/hall-effect)
- [Hall voltage](https://www.gradenine.co.uk/glossary/hall-voltage)
- [polarity](https://www.gradenine.co.uk/glossary/polarity)

## Related

- [Revision notes for IB DP Physics Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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