# EMF - Changing Magnetic Fields.

#### ben sorenson

Joined Feb 28, 2022
180
It is my understanding that a changing Magnetic Field creates an Electric Field, Thus an Electromagnetic Field.

So basically if I have a magnet in my hand and wave it around and I creating an Electromagnetic Field? If so, where does this emf get its "potential" ? Or is it not a Electromagnetic field without some sort of pickup, like a coil etc.

Or am I just all wrong and backwards.?

Joined Jul 18, 2013
28,692
Look up Flemings RH/LH rule.
What is the purpose of Fleming’s right hand rule?
It is to find the direction of induced current when a conductor moves in a magnetic field.

#### Papabravo

Joined Feb 24, 2006
21,225
It is my understanding that a changing Magnetic Field creates an Electric Field, Thus an Electromagnetic Field.

So basically if I have a magnet in my hand and wave it around and I creating an Electromagnetic Field? If so, where does this emf get its "potential" ? Or is it not a Electromagnetic field without some sort of pickup, like a coil etc.

Or am I just all wrong and backwards.?
A deep dive into Maxwell's Equations reveals that it works both ways. A changing Electric Field creates a Magnetic Field. Also since both fields are vectors, they can change by modifying their magnitude or their direction. The potential comes from the field itself.

#### crutschow

Joined Mar 14, 2008
34,455
It is my understanding that a changing Magnetic Field creates an Electric Field, Thus an Electromagnetic Field.

So basically if I have a magnet in my hand and wave it around and I creating an Electromagnetic Field?
Saying a magnetic field is "changing" means the magnetic field varies in amplitude.
Waving a magnet produces a moving magnetic field, not a varying one, so no Electromagnetic Field is created.

#### nsaspook

Joined Aug 27, 2009
13,297
It is my understanding that a changing Magnetic Field creates an Electric Field, Thus an Electromagnetic Field.

So basically if I have a magnet in my hand and wave it around and I creating an Electromagnetic Field? If so, where does this emf get its "potential" ? Or is it not a Electromagnetic field without some sort of pickup, like a coil etc.

Or am I just all wrong and backwards.?
They don't really create each other as there is only one Electromagnetic Field entity that has varying effects with matter that we say and are expressed as electric and/or magnetic fields with reactive or/and real components.

Creating is a common physics simplification but one that can't really happen as it would violate relativity with instantaneous global change.
1) A "changing" electric field CANNOT create a magnetic field
2) A "changing" magnetic field CANNOT create an electric field

https://en.wikipedia.org/wiki/Jefimenko's_equations
There is a widespread interpretation of Maxwell's equations indicating that spatially varying electric and magnetic fields can cause each other to change in time, thus giving rise to a propagating electromagnetic wave[6] (electromagnetism). However, Jefimenko's equations show an alternative point of view.[7] Jefimenko says, "...neither Maxwell's equations nor their solutions indicate an existence of causal links between electric and magnetic fields. Therefore, we must conclude that an electromagnetic field is a dual entity always having an electric and a magnetic component simultaneously created by their common sources: time-variable electric charges and currents."[8]