The property of an insulating material is the measure of how much potential difference, the insulation layer can withstand without breakdown is called as

38) The insulating material used in connecting leads of the electric heater is

39) The potential difference that causes the breakdown of insulation is called the

40) Which is the high temperature withstanding insulating material ?

41) There are two fundamental properties for insulating materials. One property is high insulation resistance. What is the another property ?