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The coil in the photos is also dramatically simplified. A real coil for the AM radio frequencies would be somewhat larger, as we saw when we built our first radio using the plastic bottle.
Often photographs show so much detail that the important parts are easily missed. By using a simplified drawing, we can accentuate the important parts of the circuit and leave out unimportant or distracting details that can interfere with getting the point across.

A simplified drawing of a circuit is called a schematic. A schematic for a simple crystal radio might look like this if drawn on a napkin at a party:

The symbol for a coil looks like a spring. The symbol for an antenna looks like someone used a coat hanger. The symbol for headphones looks like the old fashioned ear-muff style (which are great for crystal radios, since they block out ambient noise in the room). The symbol for the ground looks like what a cartoonist would draw under a cartoon character to represent the earth.

Note that the antenna is attached to the coil in the middle by a small arrow. This indicates that it is attached to a tap in the coil. An arrow is used to indicate a connection that can move, like our clip lead.

The symbol for the diode looks nothing like the little glass tube with wires coming out. Instead of represeting what the diode looks like, it represents what the diode does.

A diode is a one-way valve for electricity. The electric current flows through the diode in one direction, but is blocked if it tries to flow in the other direction. We will find out why this is important later, when we learn why the radio works. But for now, we will concentrate on building a radio that will let us hear one station at a time, with reasonable loudness.