In almost all physics books I've seen it says that the back-emf generated across inductor causes the delay in current (current is shifted 90 degrees with respect to the voltage across inductor). I just think this is wrong. There's no difference between so-called back-efm in inductor and a simple voltage drop across resistor, meaning that if we have two circuits:
1) AC voltage source + resistor,
2) AC voltage source + inductor,
then the voltage across the resistor and inductor, respectively, will be the same with respect to the source voltage! The existence of back-emf in the first case doesn't explain why the current is lagging behind the voltage across inductor.
You can agree that considering this in terms of cause and effect is pretty pointless. The back-emf is proportional to the rate of change of final current (the current that has been already modified by that back-emf). It's like an 'egg or chicken' problem. However, the formula is really simple.
One more problem here - why I think 'back-emf' is a bad name? Because it's not a electromotive force. In a circuit like 2), the Kirchoff law says the voltage across the inductor (back emf) is exactly opposite to the source electromotive force (both added give zero). Suppose back-emf was a real emf. Then there would be no current as the net emf would be zero!
Do I understand this correctly?