I do have LTSpice, Im not very good with it.

What I want is a simple way to see how voltage regulators work, to understand. For example, using iCircuit I can model this:

and see that in a 12V source circuit, with a 10kO resistor, 1.2mA of current flows, easily verifiable using Ohms law. Additionally I can see the voltage drop over the R. I can also compare that with creating a voltage divider in order to drop different values over the two R, depending on their resistance. So with 2 equal R, the voltage drop is exactly half, from 12 to 6 and 6 to 0V. The current has dropped to 600uA because of the additional equal R.

In this screenshot:

I can understand how R in parallel are different in that the first half of the circuit will have the largest current flow because its the path of â€˜least resistanceâ€™. Interestingly enough, the voltage drop across both R is total, from 12V to 0V.

Now in studying Vregs like the LM7805, I can see that:

the voltage drop across the Vreg is exactly down to 5V as it should be. I can also note that when powered by 5V, it is not enough to produce 5V because there is a Vdrop across the Vreg itself of about 1.6V if I recall correctly. Since Vin must be > Vout + 1.6V, if Vin is 5V, then Vout would be about 3.4V. So I should explore why the resulting voltage is 0V according to iCircuit instead of 3.4V. I remember seeing in the datasheet that the minimum Vin for LM7805 was 7V, so Im guessing its not outputting 3.4V just because LM7805 was designed to require at least 7V to output anything at all. Even at 6V or 7V the Vout is 0V.

At 8V I get 5V out and the current at least in the first half of the circuit is 1.35mA and the LED lights up.

At 12V I get 5V out & the current jumps to 2mA and the LED lights up. But I dont know what amperage goes out. I have no clue what EA is.

Unfortunately, iCircuit doesnt have an LM317, which I would like to understand because it combines the Vreg and the voltage divider concepts. So I did try in LTSpice but I dont know how to finish the circuit: