What is the voltage across an inductor?
simulate this circuit – Schematic created using CircuitLab
Is it Ldi/dt or -Ldi/dt? I am asking this because internet has confused me assume the RL step response of the above circuit: Since current starts rising from low values to high values it makes sense to think the voltage across L1 to have the same polarity with V1 because something has to prevent the current to go from 0 to V1/R1 at the beginning and for some time so it should be -L1di/dt but the expression of current is derived if we take VL1>0.