Difference between electronic regulator and ordinary regulator for fan

interview question:
what is the diff. btwn. electronic regulator and ordinary rheostat regulator for fans?

Answer:-

The difference between the electronic and ordinary regulator is that in electronic reg. power losses are less because as we decrease the speed the electronic reg. give the power needed for that particular speed but in case of ordinary rheostat type reg. the power wastage is same for every speed and no power is saved.In electronic regulator triac is employed for speed control by varying the firing angle speed is controlled but in rheostatic control resistance is decreased by steps to achievespeed control