What will produce a magnetic field?

Get ready for the FCC General Radiotelephone Operator License (GROL) exam. Study with flashcards and multiple choice questions, each with hints and detailed explanations. Prepare effectively for your licensing test!

Magnetic fields come from moving charges. When current flows through a conductor, the moving charges create a magnetic field around the wire, with the field looping around according to Ampere’s rule. If a DC source isn’t connected to a circuit, there’s no current, so no magnetic field is produced. A voltage across a capacitor involves charge storage on the plates, but in steady state there’s no continuous current through the dielectric, so there’s no sustained magnetic field there (though a brief magnetic field exists while the capacitor is charging). The force that drives current through a resistor causes current to flow, and it’s the actual current that generates the magnetic field, not the driving force by itself.