When a resistance of 4 Ohm is placed across the battery terminals, the current flowing is 2 amperes and when the resistance across the battery terminals is increased to 8 Ohm, the current falls to 1 ampere. The internal resistance of the battery is

28) Relation for taping English thread is given by

29) A spur gear has 50 numbers of teeth with module 2 mm. Its outside diameter is

30) Torricelli's zone in a simple barometer is

31) A workpiece of 45 mm diameter is to be turned on a lathe at 300 rpm. The cutting speed is