Thus far, we’ve seen how charge ( q ) in motion has the ability to give rise to magnetic fields ( B ) within certain material types. It will now be useful to see how certain rules are used to determine which direction this magnetic flux ( ɸ ) will travel within a given magnetic path. In particular, distinctions must be made between the conditions in which the right-hand rule and left-hand rule are used. The right-hand rule quantifies how the Lorentz force will impact a positively charged particle moving with a constant velocity ( v ) through a magnetic field:
Interestingly, the force that is imparted occurs outside of the plane that is common to +q and B, and it is at a maximum when the interaction occurs at a 900 angle. Furthermore, the positive charge in question moves through open space as opposed to the confines of a current-carrying wire. Conversely, the flow of negative charge within a conductor is ascertained via the usage of Fleming’s rule. The right-hand version of Fleming’s rule is used when a moving magnetic field is used to elicit current ( I ) in a conductor in accordance with Faraday’s law of electromagnetic induction. This application will be very useful during studies of electric generators. To the contrary, the left-hand rule is applicable to circumstances in which a wire with a pre-existing current is placed within a stationary magnetic field. The spherical path of magnetic flux is determined by pointing the thumb of the left hand in the direction of the flow of current and subsequently wrapping the fingers so that they enclose the conducting wire at hand:
In this diagram, the thumb of the left hand will coincide with the current, and the magnetic field lines coincide with the aforementioned curved fingers
Finally, when a current-carrying wire is wrapped around a metallic core, the core becomes an electromagnet. Using the left-hand rule, we can see how the metal core provides a new path in which the magnetic flux can travel:
RENAISSANCE PHYSICS 