I've recently learned a little about R-L series circuit.
Consider a simple L-R circuit, as shown in the given image- -
An inductor L is connected in series with a resistor R which itself is connected with a battery. At time t=0, the switch is closed (before that time there was no current in the circuit and the switch was opened).
Now, of course I've come across the differential equation used to find the current in the circuit as a function of time and solved it, but no matter how hard I try, i'm not able to 'THINK' about the circuit in an intuitive way (or qualitative way). I'll tell what problems I'm facing -
Firstly, let's imagine that there was no inductor in the circuit (rest of circuit was exactly same), as soon as the switch is turned ON, the current would have risen from zero to a finite value (V/R, where V is the EMF of battery and R is the resistance) instantaneously.
Now there's an inductor present, then of course at time t=0, there will be a sudden surge for the current to rise, so di/dt will be positive, the inductor will do its usual job to generate an opposing EMF. So initially, the current in the circuit will be HAVE TO BE LESS than V/R, because the EMF of the battery is being 'opposed' by that of inductor.
I fail to understand why the current in the circuit, just AFTER the switch is turned ON is zero, I mean the inductor will generate an opposing EMF but WHY this opposing EMF is equal to V in magnitude, it could be less than V, giving me a current LESS than V/R, but GREATER than zero.
My second problem is to get a 'feel' of this circuit, by 'feel', I mean to understand the circuit in a 'qualitative' manner.
Let's assume(of course I need a reason for this.)that initially the current in circuit is zero, now I have to predict what will happen to current at the next instant. For that I need to know what will happen to the EMF of the inductor at next instant (whether it will increase or decrease, remember I'm just analyzing the circuit in a qualitative way), but the EMF of the inductor is controlled by the time derivative of current, for that I need to know..... what will happen to the current at the next instant.
See? I'm struck in a circular path, again returning to my same question. This confuses me. (I hope you all can understand my problem.)
Can someone explain the behaviour of current as a function of time in a qualitative manner?