[1.] Flux, in electricity, is the effect seems to pass through a surface/substance, a concept in applied math and vector calculus with many physics applications.
Φ = F/R = NI/R
In the range power transformers work, reluctance (R) and resistance, R can be used as a constant.
If applied voltage rises, so does the magnetic field's strength.
Output voltage depends on the flux's size and how it changes overtime.
Φ and E are proportional to the turns number in the winding.