Basic Diodes/Van de Graaff generator

[Steven Ellet]

What is the name of the most basic diode?
I know that there are quite a few types of diodes, but all I want is one that will force electricity to flow in one direction and do nothing else.
________________________________________________________________
On an unrelated note, how would a Van de Graaff generator that makes a negative charge, vary from one that makes a positive charge, and how would I make one that does positive?

 

[MrSparkle]

The basic diode is just a PN-junction diode.

They won't do it at voltages created by a Van de Graaff generator. diodes have a 'reverse breakdown' voltage, at which they will freely conduct current in the opposite direction. In fact, diodes are used as protection against static electricity by having them short to ground when faced with voltages higher than the circuit is supposed to see (ie greater than 15 volts).

 

[Steven Ellet]

I thank you for answering one of my questions, however I was not implying that the two would work together, only that I wished for two answers but did not wish to make two post.

 

[Baluncore]

The Van de Graaff generator has two rollers for the belt. One is metal, the other is insulated.
I believe it is the position of those rollers, and the belt material that determines polarity.
If you swap the rollers you should change the polarity.