| a distribution of an excess of electrons or ions over a three-dimensional region, in contrast to the distribution of an electric charge over the surface of a conductor. |
| space charge n. The excess of electrons or ions in a given volume. |
space charge
electrical charge distributed through a three-dimensional region. In an electron tube, for example, a negative charge results because electrons that are emitted from the cathode do not travel instantaneously to the plate (anode) but require a finite time for the trip. These electrons form a cloud around the cathode, the cloud being continually depleted by electrons going to the plate and replenished by electrons emitted from the cathode. It is this cloud of electrons that produces the negative space charge.
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