Effect on performance of solenoid when solenoid is inside external magnetic field

NuclearUSA

I was wondering, are there significant effects on the performance of a solenoid when the solenoid is inside an external magnetic field? Does it affect the rate at which the magnetic field is established within the solenoid?

Eynstone

Welcome NuclearUSA.
If the external field is constant & the solenoid is fixed , no effect will be observed.
If the external field varies with time or the solenoid is not fastened, the rate is clearly altered ; which can be calculated by Faraday's law. Read more about inductors.

NuclearUSA

I do have another question on a related note for which I have found no satisfactory answer in the reading I have done on the subject. Say we have two identical air-core solenoids that are placed face-to-face. The coils are then connected in parallel with an alternating current source. Since the coils are identical, the current flowing through them should be identical. How will the inductance of this circuit compare with a circuit composed of a single solenoid of equal dimensions to the previous set combined (2x the length of one of the original's and everything else the same).

NuclearUSA

I have done reading on mutual inductance, but the definitions and equations given are quite cryptic and I am not sure how to use them in calculations.