The adjective is electric, because it is describing the heater.
The pie exploded when the cows flew away
The size of a space heater depends on the size of a living room or bedroom. The best size for a space heater is 150 sq. ft for living rooms and bedrooms.
Yes, it is. It can be both a noun or an adjective, referring to the gender of a living thing.
It is difficult to believe that anything has a 100% efficiency rating, even an electric heater. Electricity is very good at producing heat. Any loss of efficiency would be in how much heat is lost to the surrounding equipment and building structure in the immediate vicinity of the heater, which may be in the basement, as opposed to heating the air in living or working areas which is probably what you want. Electricity is very expensive when compared to other forms of heat, such as natural gas.
No
bustling
See website: Atomic bombings of Hiroshima and Nagasaki. people living there died.
Deceased is used as an adjective and a noun. Adjective: no longer living. Noun: a dead person.
No, it is not. It is a noun meaning an occupation, or way of making a living.
a field of electricity created by a living organism
yes
Breathing is usually a verb, but can be used as an adjective, as in, "He was a living, breathing paragon of fatherhood."