It's a fun calculation, but if the magnet is at 10GV it would need to use a minuscule current to avoid blowing up or melting down (P=I·U, so 1µA·10GV = 10kW), w

It's a fun calculation, but if the magnet is at 10GV it would need to use a minuscule current to avoid blowing up or melting down (P=I·U, so 1µA·10GV = 10kW), which in turn makes for an equally minuscule magnetic field (multiplied by unspecified number of windings). A powerful (superconducting) magnet would use lots of amps, but almost no volts, otherwise it would generate lots of heat.