What causes the oscillation that generates the waves in an electromagnetic field? I'm reading "The Feynman Lectures" regarding electromagnetism. I'm having a problem understanding what exactly disturbs the electromagnetic field and generates the waves.
I assuming the field is usually in equilibrium and adding protons would create a potential for the electrons to move towards them.
But how do you actually add them, where do they come from?
Also, in order to have a wave, something must be oscillating. What's oscillating in this case?
Sorry for the very beginner question, I just want to fully understand the process before moving on.
 A: 
I assuming the [electric] field is usually in equilibrium and adding protons would create a potential for the electrons to move towards them. But how do you actually add them, where do they come from?

At the beginning of electricity observations and use were some inventions:


*

*a lot of different working electrostatic generators to separate electric charges

*the Leiden jar to store separated electric charges 

*Voltaic respectively Galvanic cells and Batteries, which are electrochemical cells that derives electrical energy from spontaneous redox reactions taking place within the cell.


 
In all that cases the electrons are the easier to move charges and they are the one which flow through the wires during separation or during the process of re-equilibration.
The best adoptable invention to our modern live was the electric dynamo, in our days called electric power generator, and the electric motor. Both devices based on the discovered phenomenon of the electromagnetic induction.


Generating an EMF through a variation of the magnetic flux through the surface of a wire loop can be achieved in several ways:
    
    
*
    
*the magnetic field B changes (e.g. an alternating magnetic field,
    
*or moving a wire loop towards a bar magnet where the B field is stronger),
    
*the wire loop is deformed and the surface Σ changes,
    
*the orientation of the surface dA changes (e.g. spinning a wire loop into a fixed magnetic field),
    
*any combination of the above. (from Wikipedia)
    
  

To your next question:

Also, in order to have a wave, something must be oscillating. What's oscillating in this case?

There are alternating currents and direct currents. In the last nothing is oscillations, simply the electrons from a DC generator or a battery are flowing from the source to the sink. In alternating currents a generator converts the rotation of a shaft with coils and an applied magnetic field (or vice versa) into an oscillating potential and the electrons in the wire get pushed forth and back.
Any acceleration of charges is accompanied by electromagnetic radiation, the electrons emit photons. This is a non suppresable process. Whenever electrons are running inside a coil and even if a body is accelerated, the electrons radiate.
This phenomenon of EM radiation was adopted to send informations around the globe. Radio waves are made in a radiating antenna rod by the help of an electric generator which pushes the electrons inside the rod forth and back. A receiver gets tuned to the same frequency as the sender and the sender modulated on the carrier frequency the informations which the receiver transformed back to music or a data stream.

I'm having a problem understanding what exactly disturbs the electromagnetic field and generates the waves.

Quantum mechanics was developed to describe processes inside the atoms:


Quantum mechanics ... is a fundamental theory in physics which describes nature at the smallest scales of energy levels of atoms and subatomic particles. (Wikipedia


Apart from the introduction of these QM theories about an overall existing EM field in practice one could measure


*

*local acting electric fields (from the separation of electric field),

*local acting magnetic fields (from permanent magnets or from accelerated in circles  charges),

*electromagnetic radiation from the emission of photons and as a special case

*EM waves (radio waves) as modulated EM radiation.

A: It is not necessary to add charges to a system in order to generate electromagnetic waves.  EM waves are caused by the acceleration of charges, typically of charges that are already in the system.  There are many, many ways to accelerate charges.  A simple way is to produce an alternating current in a wire loop by, for example, spinning it rapidly in a stationary magnetic field on an axis that is in the plane of the loop and perpendicular to the direction of the magnetic field.
An EM wave does not need to oscillate in the ordinary sense of the word "oscillate". An electromagnetic pulse could be caused, for example, by sudden and brief acceleration of a charge to a high velocity (so that the acceleration occurs in just one direction). However, the pulse can be decomposed into (oscillating) wave forms covering a continuous range of frequencies. Running the pulse through a prism or diffraction grating will separate the frequency components. Neither pulse nor components are caused initially by oscillating charge, only by that briefly accelerated charge.
