Is velocity ratio of a machine affected by applying oil on it?Explain with reason. ​

It depends upon SAE No. of oil. (SAE means Society of Automotive Engineers). However, it usually does protect against friction.

Explanation:

If we use very viscous oil, it does not reach all the parts. Very thin oil will flows away easily and gets wasted. Grease is used in such cases. It is generally used around ball-bearing. Normal grease or oil is never used where there is high pressure, high temperature and high speed. Special lubricants are used in such cases. In cold season the oil becomes thick and in hot season it becomes thin. Therefore selection of lubrication also depends on the season. It is always advisable to refer operating manual of the equipment before selecting the lubricant.

The intensity of friction depends on following factors:

i) The area involved in friction.

ii) The pressure applied on the surfaces.

Force = Pressure ´ Area Frictional force will increase, if the area of contact will increase or if pressure applied on the surface increased.

the current is 0.6

voltage ÷ resistance = current

so 12 ÷ 20 = 0.6