Conductive atom force microscopy observations have been performed on carbon nanotube networks. The results indicate that within an imaging range of several tens of micrometers the resistance of a carbon nanotube is much smaller than the contact resistance between two crossed carbon nanotubes and so the potential difference hardly appears along a carbon nanotube if the carbon nanotube network is electrically biased. Besides, if several semiconducting carbon nanotubes wind into a bundle, they tend to appear like metallic carbon nanotubes.