In a multiple choice question a simple circuit of only a battery and an inductor the length of the inductor is doubled. The question is how does the velocity of the electrons change. Big spoiler alert: the velocity decreases.
My reasoning was that in the equation $V=-\dot{I}L$ the inductance doubles so the change in current must halve in order for the voltage to remain constant. Thereby the current and the velocity of electrons decreases. Is this correct so far? Because the solutions say: inductance increases so the resistance increases and (by Ohm's law I guess) the current decreases. However, I do not understand why the resistance (there is no resistor) should change if the inductance increases?
[Physics] Resistance of an inductor in direct current
electric-circuitselectric-currentelectrical-resistanceinductance
Best Answer
In real life an inductor consists of a coil of wire (with or without a laminated iron core). So a real inductor has both resistance and inductance. If you double the inductance by increasing the length of wire on the coil, then the resistance will increase (roughly 1.4 times). All the same, your question should have made it clear that you were dealing with a real inductor, not an ideal or 'pure' inductor. And it should also have told you that the inductance is doubled by adding more turns to the coil.
Your question should also have made it clear whether it wanted a comment about electron drift velocity just after the inductor is connected to the battery, or after a steady current is achieved. Your answer is suited to the former (though it looks as if you should include a resistive term in your equation); their answer will also apply in the latter case, though, as I've said, I think they should have warned you that it was not a pure inductor.
You'll have gathered that I don't think much of the question!