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The plasma appears electrically neutral from the outside because it contains approximately equal amounts of positive and negative charges, whose effects cancel each other out. The denser the plasma, the smaller the distance (called the Debye length) over which quasineutrality occurs. Plasma in a tokamak is quasineutral over distances of less than 1 mm, whereas in interplanetary space it can be tens of metres. However, unlike a neutral gas, plasma responds to electric and magnetic fields and electric currents can be generated in it. The term quasineutrality comes from the Latin “quasi”, which means “as if” or “resembling”.