Why do moving charges radiate energy?

Moving charges radiate energy due to the acceleration or deceleration causing a disturbance in the electromagnetic field.

In more detail, the phenomenon of moving charges radiating energy is a fundamental concept in physics, particularly in the study of electromagnetism. When a charge is in motion, it creates an electromagnetic field around it. If this charge is accelerated or decelerated, it causes a disturbance in this field. This disturbance propagates outwards in the form of electromagnetic waves, which carry energy away from the charge. This is the energy that we refer to as being 'radiated' by the moving charge.

The concept can be understood better with the help of Maxwell's equations. These equations, formulated by James Clerk Maxwell, describe how electric and magnetic fields interact. One of these equations, the Maxwell-Faraday equation, states that a changing magnetic field induces an electric field. Similarly, a changing electric field induces a magnetic field. When a charge accelerates or decelerates, it causes a change in the electric field, which in turn induces a change in the magnetic field. This interplay between the electric and magnetic fields results in the propagation of electromagnetic waves.

The energy carried by these waves is proportional to the square of their amplitude. This means that a greater acceleration or deceleration of the charge will result in a larger disturbance in the electromagnetic field, leading to the radiation of more energy. This is why, for example, an electron moving in a circular path (as in an atom) does not radiate energy, because its acceleration is centripetal, i.e., it is always at right angles to the direction of motion. However, if the electron is jolted out of its stable circular path, it will accelerate in a non-centripetal manner and will radiate energy.

In conclusion, the radiation of energy by moving charges is a direct result of the disturbances caused in the electromagnetic field due to their acceleration or deceleration. This is a fundamental concept in electromagnetism and is described by Maxwell's equations.