Högerregel

Högerregel, or the right-hand rule, is a mnemonic used in physics to determine the direction of a vector produced by a cross product and to find the direction of magnetic fields and forces in electromagnetism. It relies on the orientation of a right-handed coordinate system.

Common forms of the rule include several practical variants. For a cross product a × b, one version states that if you point the index finger in the direction of a and the middle finger in the direction of b, the thumb points in the direction of a × b. An alternative version asks you to curl the fingers from a to b; the thumb then indicates the direction of a × b. For the magnetic field around a straight current-carrying wire, the rule is applied by gripping the wire with the right hand so that the thumb points along the conventional current; the curled fingers show the direction of the magnetic field around the wire. For a solenoid, curling the fingers in the direction of the current around the coil and extending the thumb along the coil’s axis gives the direction of the magnetic field inside the coil.

The rule also clarifies the Lorentz force on a moving charge, F = q v × B: the direction of the force on a positive charge follows the right-hand rule, while the force on an electron is opposite due to the negative charge. Its use presumes a right-handed coordinate system and is widely taught in physics education as a consistent method to infer spatial directions from vector relations.

The term Högerregel is used in several Nordic and Germanic languages (for example högerregeln in Swedish) to refer to this group of rules, reflecting the same geometric principles across languages.