# A coil connectd to AC voltage source

Suppose I connect an AC voltage source (frequency = 7hz) to a coil, the coil will resonate and radiate an electromagnetic wave. What's the frequency of the radiated wave and does it depend on the dimensions of the coil and its number of turns? Thanks!

the coil will resonate

To make a coil resonate it must be tuned with a capacitor so no, it is very unlikely to resonate

the coil will resonate and radiate an electromagnetic wave.

At 7Hz there will be virtually no electric field other than what the AC voltage source is generating whether it connects to the coil or not.

What's the frequency of the radiated wave and does it depend on the dimensions of the coil and its number of turns?

The frequency of the radiated magnetic field is the same as the frequency of the AC excitation, 7Hz. The frequency is fixed by the incoming AC and has nothing to do with the coil construction.

Unless you have an enormous piece of wire you are not going to radiate any significant electromagnetic waves at 7 Hz. What you will create is a magnetic field.

The construction of the coil will affect the arrangement and strength of the magnetic field and also how much current will flow. The choice of air core or iron core will affect the linearity of the current flow.

As Andy said resonance is quite a separate topic from radiating electromagnetic waves or indeed magnetic fields.

• Please check what you said about saturation - "unless your coil is wrapped around a suitable iron core the magnetic field will become saturated" – Andy aka Feb 24 '14 at 12:28