Electricity basics - Induction

An electron flow - a current - in a conductor can influence the electron spin in neighboring conductors, which in turn yields magnetic fields, as we saw with the solenoid. However, this relationship goes both ways. Magnetic fields can also cause electron flow: if we move a conductor through a magnetic field, the magnetic field will push the electrons in the conductor in a certain direction. Recall that we learned in previous posts that it is voltage that makes current flow. The push - or pressure, if you will - that we exert on the electrons in the conductor by moving it through a magnetic field is also voltage. However, contrary to the voltage that we observed in earlier posts, this voltage is not caused by the difference between two differently charged nodes, as with batteries. In the case, voltage is caused by a force called electromotive force . The end goal - or rather, the result - is nevertheless the same: a current occurs! Now, if we move the conductor through the magnetic field in the opposite direction, the polarity of the voltage and the direction of the current change too. This phenomenon, when a magnetic field influences a conductor so that electric potential occurs, is called induction . One prerequisite for induction is that either the magnetic field or the conductor actually moves.

Source: https://adityaabeysinghepresentations.blogspot.com/2013/11/electromagnetic-induction.html?m=1 (2026-09-09)

Current and voltage that regularly changes direction and polarity is called alternating current, shortened AC, and the opposite is called direct current, or DC.

The magnitude of the induced voltage is subject to:

• the length of the conductor that "cuts through" the magnetic field lines
• the velocity at which the field lines are "cut"
• the density of the magnetic field

If the conductor in which we have induced voltage is part of a closed circuit, the voltage is going to drive current through the circuit. As we already know - both from earlier posts but also from above - current causes magnetic fields to appear around the conductor that leads it. This means that there are two magnetic fields present at induction: one between the poles of the magnet that induces the voltage/current and one around the conductor that we move back and forth between the poles of the magnet. The direction of the induced current - and thus the direction of rotation of the magnetic fields around its conductor - is such that it "collides" with the direction of movement that is otherwise required for the induction to happen. This "collision" or "friction" is similar to what happens when you try to make two magnets of the same polarity touch: they repel! This phenomenon is described in greater detail in Lenz's Law, but to summarize: the kinetic energi required to move either the magnetic fields past the conductor or the conductor through the magnetic fields is converted into electric energy.

To be continued. Meanwhile:

1. Are there better expressions in English than "cut" and "cut through" magnetic fields?
2. I translated the book to saying "density of the magnetic field", but I am unsure whether this is correct in English. Would "intensity" be better?
3. I feel uneasy (really intrigued!) when the book makes a connection between kinetic and electric energy, because it makes me wonder: are there conversion tables or the likes? As in, how much power in watts, joules or even calories yields how much electric energy? Wouldn't that depend on the mass of the, say, inductor that is forced through the magnetic fields? Wouldn't the strength of the magnetic fields also be a determining factor? Leading, in my head, to the definition: if a conductor of X mass moves through magnetic fields of Y strength with the velocity of Z, then V volts and A amperes are induced.
4. In other places, I have seen "potential difference", "electromotive force" and "voltage" being used interchangeably. But after reading the section about induction in this book, it does make me want to separate at the very least the phrases that distinguish how voltage is achieved: by opposite charges (such as in a battery) or by electromotive force as seen in induction...
5. I was absolutely blown away when I understood what induction is! So much of our appliances seem to be using this technology! Like, the spinning bikes at the gym? I can just imagine there being a bunch of magnets surrounding the wheel looking "outwards", and pieces of iron all around the wheel itself looking "inward" and as I pedal, the rotation of the wheel induces voltage/current, which turns on the display?! Again, I'm so amped about this. 😆🩷