The tendency nowadays is to use synduction or synchronous motors. The synduction motor resembles an induction motor but runs at synchronous speed.

The correct answer is Resistance Heating. Resistance heating is based on the I2R effect and is highly resistive in nature that's why it has the maximum power factor. Electric resistance heating is defined as “the heat produced by passing an electric current through a material that preferably has high resistance”.

Acetylene is the only fuel gas suitable for gas welding because of its favourable flame characteristics of both high temperature and high propagation rates. Other fuel gases, such as propane, propylene or natural gas, produce insufficient heat input for welding but are used for cutting, torch brazing and soldering.