<Tr> <Td> Electrical network (hide) <Ul> <Li> Electric current </Li> <Li> Electric potential </Li> <Li> Voltage </Li> <Li> Resistance </Li> <Li> Ohm's law </Li> <Li> Series circuit </Li> <Li> Parallel circuit </Li> <Li> Direct current </Li> <Li> Alternating current </Li> <Li> Electromotive force </Li> <Li> Capacitance </Li> <Li> Inductance </Li> <Li> Impedance </Li> <Li> Resonant cavities </Li> <Li> Waveguides </Li> </Ul> </Td> </Tr> <Ul> <Li> Electric current </Li> <Li> Electric potential </Li> <Li> Voltage </Li> <Li> Resistance </Li> <Li> Ohm's law </Li> <Li> Series circuit </Li> <Li> Parallel circuit </Li> <Li> Direct current </Li> <Li> Alternating current </Li> <Li> Electromotive force </Li> <Li> Capacitance </Li> <Li> Inductance </Li> <Li> Impedance </Li> <Li> Resonant cavities </Li> <Li> Waveguides </Li> </Ul> <Li> Ohm's law </Li> <Tr> <Td> Covariant formulation (show) <Ul> <Li> Electromagnetic tensor (stress--energy tensor) </Li> </Ul> <Ul> <Li> Four - current </Li> <Li> Electromagnetic four - potential </Li> </Ul> </Td> </Tr>

Which of the following causes a current in an electrical circuit