<em>Installing interpoles in armature core helps to cut down the spark in DC generators. </em>
Explanation:
A dc generator has a split ring type commutator to convert ac current generated to dc. The commutator comes in contact with the brushes throughout the working of the generator. Sparks occur in this region of contact.
When current flows through the armature coil it produces armature flux which opposes the main flux. This is called armature reaction and is the reason for sparks.
Interpol's are small auxiliary poles placed between the main poles of the generator. They are wound by wires of a number of turns connected in series with the armature. Interpol's produce a field that cancels the magnetising field of the armature and thus cancels armature reaction.
I think when particles are in the gas form they are most likely to cause a chemical reaction considering the fact that gas particles aren't very controllable and it would make sense that they would react unexpectedly
