ICSE Class 10 Answered

Above paragraph is related to the electrolytic reduction of alumina.

As you know about electrolysis process, the same principle is applicable here in this case.

When we supply electricity, electric current is passed through an electrolyte, but when the concentration of the electrolyte is decreased with deposition of metal on cathode which resistance in the flow of current.

Now the question is how we come to know that the whole electrolyte is consumed or its concentration is decreased.

now the solution for this, we used a high resistance bulb in the circuit of electrorefining, this bulb acts as an indicator, whenever the concentration of electrolyte will decrease it will start glowing, which indicates that its time to add the electrolyte i.e., molten aluminium oxide for the continuation of the process.