Coils in a Crystal Radio

Why is the second coil important? Or what does it allow the radio to do?

The second coil in a crystal radio is important because you can use it to select the waves from whichever radio station you want, and you can use it to tune the sound of the radio. This allows the radio to play whatever you want, however you want.

What is the second coil called?  

The second coil is called the tuning coil.

What would happen if you only had one coil?  

If there was only one coil, you would have to find another way to tune the radio waves, doing this could mess with the volume, and it could not let you be able to hear anything clearly or at all through the earpiece.

What is the downside of having two coils?  

In order to not lose volume with the transfer from the smaller coil, to the magnetic waves, to the tuning coil, you can move the two coils closer together, but this means that more radio waves can get through, so it is a “trade-off”.