What is the use of parallel lines on rear glass of car?






 It is called as defroster.

Usually there’s a switch on the dash to turn on the system and it will run for a specified time then turn off automatically. 
There may be an icon on the dash or the switch itself illuminates when the rear window defroster is operating. The amount of heat produced by the grid is relatively low …just enough to raise the temperature to evaporate any dew or melt any ice …so it’s not like you’re gonna burn your hand if you touch the glass while the system is working.

It is just same as the Defogger used by us when there is mist on the windshield. The grid lines are made up of resistive conductors in or on the glass, generally they are very fine wires that are baked or sometimes embedded onto the inside of glass surface. In these lines when current is passed, due to resistance the glass heats up and removes the mist so that the driver get a clear view in the rear view mirror .

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