Can anyone explain about magnetic field in solenoid excited by AC?

Question

when DC is used to excite a solenoid, the poles (north and south) can be found using end rule...
incase of solenoids excited by AC, how are the poles formed?
Do they change each other for every half-cycle of the input excitation AC? (i.e., north becomes south and south becomes north in every following cycle)

Answer 1

The simple answer to your question is yes they do reverse every half-cycle.However, dependent on other elements(e.g. capacitance in the circuit), there may be a delay between the input voltage signal and the electromagnetic field strength output

Answer 2

Not for a "short-term" terraformation (tens of thousands of years). An Earth-like atmosphere would itself shield an surface life from cosmic radiation - the lack of a magnetic field would become serious only over time as the solar wind and cosmic rays stripped the atmosphere away, as is believed to have actually occurred in Mars's history. As has been mentioned above, the magnetic field problem is likely a rounding error in the cost of terraformation, and totally irrelevant over time frames as great as any past human civilization has existed.

Answer 3

END rule? Or Left HAND rule? Anyway, yes, the polarity of an AC coil reverses with every half-cycle. Such coils were typically used in the old style rotary telepone bell ringer circuit.

Answer 4

Yes but for ac there is a dampening coil that will hold the relay closed while the current is off. If u apply ac to a dc relay it will chatter and will cause a problem. U must use ac relays in ac.