Taking the electronic charge as ' e ' and the permittivity as ′ ϵ ′ 0 , use dimensional analysis to determine the correct expression for ω p . √ N e m ϵ 0 √ N e 2 m ϵ 0 √ m ϵ 0 N e 2 √ m ϵ 0 N e be obtained by heating?