>>2927973
Yes. I think the resistors are superfluous for 500mA or less power draw. Though most phone chargers will provide more than that current with no resistors, as far as I understand.

>>2927981
How the hell is a shunt inductive? It’s just a piece of straight metal with a known resistance, pic related. Heck, you could even just use the wire itself as a current sense resistor, though if you care about absolute accuracy you’ll need to compensate for the temperature of the wire.

A core is used for a current transformer because of the way magnetic flux flows. With the right-hand-grip rule, magnetic flux wraps around the conductor, it does not move coaxially to the conductor. If you wrapped thin wire around the conductor, the magnetic flux would be wrapping around alongside the thin wire, while the thin wire would only be able to pick up magnetic flux running down the conductor. Those are orthogonal, you wouldn’t sense anything. If you put a toroidal core around your conductor, the magnetic flux from the conductor will wrap around inside that toroid. Thin wire wrapped around this toroid would perfectly pick up that magnetic field.