Which of the following materials allows charges to flow easily?
a. wood
b. an electrical conductor
c. glass
d. an electrical insulator

Option (B) is the correct answer.

Explanation:

A conductor which allows the quick or easy movement of charges through it is known an electrical conductor.

For example, copper is a good conductor of heat and electricity.

Whereas wood is a non-conductive substance as it does not allow the movement of charges through it. Thus, wood is a non-conductive in nature.

Glass is a poor conductor of electricity as it inhibits the flow of free movement of electrons through it.

Insulators are the substances or material in which there is also no movement of electric charges or very little movement of electric charges.

Thus, we can conclude that out of the given options, an electrical conductor allows charges to flow easily.

if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask

if they have a finite resultant