Since there may also be voltage dependence in other factors in a Fowler–Nordheim-type equation, in particular in the notional emission area A r and in the local work-function, it is not necessarily expected that κ for CFE from a metal of local work-function 4.5 eV should have the value κ = 1.23, but there is certainly no reason to expect that it will have the original Fowler–Nordheim value κ = 2.