A resistor or an inductor. The inductor limits transient current, not steady state current.

-- If the excitation source is AC, then the steady state of the circuit depends on

the voltage, frequency, and waveform (harmonic content) of the source.

-- If the excitation source is DC, then the steady state current in a series circuit

is zero. DC doesn't pass through a capacitor.

No, the current has to change for a voltage to be induced in the transformer.

Watts = Current x Voltage x Power Factor

If you are talking about 120 VAC and a pure resistive load (Where Power Factor = 1) then the steady state current is about 8.3 Amps. So you are okay.

If you had a conductive load with a Power Factor of .5 then the current would double. The steady state current should be no more than 80% of the breaker rating. Therefore, the steady state current should be less than or equal to 16 amps.

No. A constant DC current of sufficient magnitude

induces smoke in a transformer.