The voltage-arc length characteristic of a $$DC$$ arc is given by $$V=20+40L.$$ where $$L=$$ arc length in $$cm.$$ The power source characteristics can be approximated by a straight line. Open circuit is $$80V$$ and short circuit current $$1000$$Amps. The optimum arc length in $$mm$$

Thrust force in drilling can be reduced by .................A............... the point angle and by ..........B.......... the helix angle of the drill

(a) increasing / reducing
(b) increasing / reducing

Increase in rake angle causes ..........A................ in chip thickness and .............B......... in shear angle

(a) increase / reduction
(b) increase / decrease

Amount of energy consumption for unit volume of metal removal is maximum in