Can magnetic fields occur without an electric field?

[TheAspiringDoc]

Hi,
In class today, students were given the task to make a poster about electromagnetic waves. one of the criteria was to explain how electromagnetic waves were created, and one of my classmates answered 'they are formed when an electric field meets a magnetic field'. I believed this was wrong and i consulted my teacher, who is very knowledgeable, but fortunately when they don't know the answer they don't just make something up, nut they say they don't know. So, I thought i'd ask AN. first up, Can a magnetic field be created without an electric field?, secondly, can a magnetic field exist away from an electric field as described by my classmate?, thirdly, do magnetic fields technically exist? also, where does the right-hand slap rule fit in?

[lzxnl]

Hi,
In class today, students were given the task to make a poster about electromagnetic waves. one of the criteria was to explain how electromagnetic waves were created, and one of my classmates answered 'they are formed when an electric field meets a magnetic field'. I believed this was wrong and i consulted my teacher, who is very knowledgeable, but fortunately when they don't know the answer they don't just make something up, nut they say they don't know. So, I thought i'd ask AN. first up, Can a magnetic field be created without an electric field?, secondly, can a magnetic field exist away from an electric field as described by my classmate?, thirdly, do magnetic fields technically exist? also, where does the right-hand slap rule fit in?

Interesting question. From my knowledge, you can have a magnetic field without an electric field. An electric field requires the presence of charges to set up but a magnetic field doesn't. Neutrons, for instance, possess a magnetic dipole moment but zero electric charge, so theoretically if you got a whole bunch of neutrons and put them together (sort of hard as they're unstable by themselves), they'd create a huge magnetic field with no electric field as they're uncharged.

As for 'creating' a magnetic field, however, magnetic fields rely on either the intrinsic magnetic properties of particles (like how iron is magnetic due to its magnetic domains that are themselves magnetic) or the presence of an electric field. The movement of charge, as I'm sure you know, generates a magnetic field and this normally requires an electric field (not always). In addition, electromagnetic induction also produces magnetic fields from changing electric fields.

Disclaimer: special relativity shows that magnetic and electric fields are actually the same thing, which makes sense if you look at the formula for the magnetic force. It appears to be velocity dependent. Imagine if you have two observers and a moving charge in a magnetic field. Let's say one of the observers is moving with the charge, so it doesn't see the charge as moving. If the charge is moving at a constant velocity, both observers must measure the same force. Now, the first observer sees the charge moving, so it can be affected by the external magnetic field set up. However, the second observer moving with the charge can't see the charge moving, so the second observer doesn't see a magnetic force. It turns out that the second observer sees an ELECTRIC force acting on the particle instead; electric and magnetic fields are simply the same phenomenon measured by different people.