State advantages and disadvantages of expansion of solid

One of the most useful use of expansion by heat is for switches on many types of machinery and home appliances Thermostats in the millions of cars are operated by using the expansion of metal Thermometers are another example,

The disadvantages are just as common Railway lines need free movement d will buckle without sufficient clearance. Internal combustion engines need to be designed to allow for expansion and contraction of metal parts

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.