How Do the Units Work With Faraday’s Law?
Faraday’s Law is sort of a big deal. It says that a changing magnetic flux creates an electric field. This electric field then creates a change in electric potential around a closed loop (we often call this an electromotive force — EMF). As an equation, it looks like this.
Oh wait! What about the negative sign? OK, I’m not a huge fan of the negative sign in this equation since it’s sort of meaningless. It works with the integral form of Faraday’s Law, but here is it’s just a pointless gesture. Anyway, it doesn’t have a units anyway. Also, there is that “N” for number of loops. I get that one, but it also doesn’t have units.
So, on the left side we have the electromotive force. That has units of Volts. But what about the right side? Oh, sure the time change is in seconds — but what about flux? Magnetic flux is defined as:
Yes, this is just an expression for the magnetic flux for a constant magnetic field over a flat area. It doesn’t matter. Only the units matter. The cosine function is simple. It has no units since it’s a ratio of the sides of a triangle. Area is easy also. If we are using normal units (and we are) then it would just be in units of square meters (m²).
The magnetic field is more difficult. This is measured in units of Tesla. But that doesn’t really mean much. Here is the key. We…
