Engineering KVL for a RLC circuit given current direction and polarity o

[cnh1995]

But then the current will go in the negative terminal of the inductor if the polarity is switched though?

Inductor is acting as a voltage source. What is the direction of current inside a voltage source?

 

[Aristotle]

Inductor is acting as a voltage source. What is the direction of current inside a voltage source?

Umm..the electric current through a voltage source is out of the positive terminal if it's supplying power.

 

[gneill]

In that case, current flows out of the positive terminal when a capacitor is discharging then?

Right!

Also knowing that the voltage across the inductor does not change instantaneously as well, the polarity remains the same as when the voltage source was applied to the circuit before t=0 correct? (+) on top and (-) on bottom?

It's the current that doesn't change instantaneously for an inductor. The inductor will produce any potential across itself required in order to maintain that magnitude and direction of current flow. That means the potential across an inductor can change instantaneously.

In this instance, just before the switch is opened the current was flowing downward through the inductor, and the potential across it was zero (steady state, constant current for an inductor). When the switch opens, the inductor "wants" to maintain the flow and direction of its current. So it reacts by producing a potential across itself that tends to maintain the status quo, driving the current in its current direction. The potential created can have either polarity depending upon the requirement to maintain that flow. In this case the potential would be higher at the bottom of the inductor than its top.

Note that components other than sources do not have inherent polarities. You can turn passive linear components end-for-end in a circuit and they will behave the same.

 

[cnh1995]

Umm..the electric current through a voltage source is out of the positive terminal if it's supplying power.

Yes. So shouldn't + be at the bottom?

 

[Aristotle]

Right!

It's the current that doesn't change instantaneously for an inductor. The inductor will produce any potential across itself required in order to maintain that magnitude and direction of current flow. That means the potential across an inductor can change instantaneously.

In this instance, just before the switch is opened the current was flowing downward through the inductor, and the potential across it was zero (steady state, constant current for an inductor). When the switch opens, the inductor "wants" to maintain the flow and direction of its current. So it reacts by producing a potential across itself that tends to maintain the status quo, driving the current in its current direction. The potential created can have either polarity depending upon the requirement to maintain that flow. In this case the potential would be higher at the bottom of the inductor than its top.

Note that components other than sources do not have inherent polarities. You can turn passive linear components end-for-end in a circuit and they will behave the same.

Wow that makes sense now ! I just realized I got the terms mixed up between inductor and capacitor. Inductor's CURRENT doesn't change instantaneously, but its voltage can.

Thank you so much for being helpful gneill and cnh1995!