# $RL$ circuit and pure inductor

When a dc voltage source is connected with an ideal inductor we get a linear change/increase in current in inductor with respect to time.

But when we add resistance in series with inductor and apply dc voltage we get exponential increase in current in the circuit and so the change in current is not linear now.

What is the reason behind that?

I wonder how a resister can modify the rate of change of current in an inductor or circuit? Resistor just decreases the current in the circuit, what it has to do with the shape of the current or current change?

The sudden increase of current in the inductor produces a self-induced electromotive force, $$V_{emf}$$, opposing the current change. This appears as a Voltage across the Inductor, $$V_L = - V_{emf}$$. This $$-V_{emf}$$ will slow down the current change, and in turn, the slow down of the current change will make $$V_L$$ become smaller.