Hi all, This one's an easy one: What's the easiest way of telling whether a current is "enclosed" in a closed path or not? And how can I tell when a current effectively cancels itself out? For example, let's say I have a spherical shell with surface current density K [A/m], and I want to find H outside the sphere. Would this be 0 because whatever total current is over the sphere, the current flowing would eventually cancel each other out. Is this a valid assumption, even for K not constant? Would the reasoning for something like this be similar to the reasoning for H = 0 outside a solenoid (approximately!) and a toroid? Any clarifications would be appreciated!