Suppose we have a simple RL circuit. At $t=0$, I close the switch so that current starts flowing in the circuit. When the steady state is achieved, current $i=\frac{\epsilon}{R}$ would be flowing in the circuit due to which an energy $\frac{Li^2}{2}$ will be stored in the magnetic field lines on inductor. But as soon as the switch is opened, the current would become $0$, which make the magnetic field lines disappear suddenly, which according to Faraday's law must induce an emf. But as the circuit is open no current will flow in it (according to my teacher, charge can never accumulate in a circuit. So if current flows in open circuit, it would mean that charge is accumulating in it). If there is no current how can the energy in magnetic field lines disappear suddenly? Isn't this a voilation of law of conservation of energy?
Ps: I read the answer given in a similar question Where the energy stored in magnetic field goes? but I kinda disagree with the point that in superconducting coil, current will keep flowing because according to Prof. Walter Lewin, no electric field can exist inside a superconducting coil, so current cannot exist in the coil. Only surface currents must exist.
[Physics] Where does the energy stored in inductor go on opening the switch
electric-circuitselectric-fieldselectromagnetic-inductionelectromagnetisminductance
Best Answer
This is a situation where the simple rules are insufficient. You simply cannot analyze that circuit any more than you can solve x+2=x+3. What happens in the real world is that the inductor creates enough emf to form a spark in the switch. This means the switch no longer acts like an ideal switch.
In the real world, we call this effect "flyback.". It can damage components, so we typically design circuits to prevent this from occuring. For example, it is common to see a flyback resistor in parallel with the inductor on large motors. It gives the current somewhere to go.