Hi there, I have a question about the definition of a charge of a free electron. Let's suppose that QED is the true theory of the interactions of charged particles. Presumably the charge on an (effectively) free electron, then, is the charge on an electron in which the electromagnetic interactions have been turned off -- ie, the coupling constant e is set to zero. But since, as well as being the coupling, e is also the charge on an electron, how can there be any charge on a free electron?! Sure the answer here is obvious, but any help much appreciated!