Resistors work with current flowing in any direction.

If you phrase the lamp setup differently it makes sense.

Each lamp has a 6 volt drop from one terminal to the next. If you connect them in series you have three 6V drops, so you need 18v to drive that circuit.

Yes, but to properly drive the circuit you need to supply 18V. The bulbs were intended for 6V (well, close to that, but for this teaching purpose lets keep the math simple). That's why I phrased it the way I did.

To elaborate on what Mbecker is saying, the total voltage drop of one of your battery circuits above will always be equal to the voltage of the battery. The circuit WANTS to be at equilibrium. So if you have two lamps in series on a 9V battery, there will be approximately a 4.5V drop on each bulb.

It's going to be tough for you to outdo something that already exists like Sparkfun's tutorials.

Here is just a sampling of the beginner ones:

https://learn.sparkfun.com/tutorials/voltage-current-resistance-and-ohms-law

https://learn.sparkfun.com/tutorials/series-and-parallel-circuits

https://learn.sparkfun.com/tutorials/resistors

https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter

Another good way to think of a capacitor is to think of them as a short when they are empty, and an open when they are full.

I won't spoil the "bulb burned out" exercise, but a hint for the guys learning, you have to have current flowing for a voltage drop. Google Kirchoff's voltage law to learn some basic analysis of a circuit like that.

If you ignore all the math of when it's charging/discharging, like a beginner hobbyist would do when using a cap to decouple power supply lines, you can pretend a capacitor is a switch.

When the capacitor is fully discharged, it acts like a shorted out (closed) switch. When it is charged to the input voltage level, it acts as a open switch. In between it acts a little differently.

Look at this link at the applications section for a bypass capacitor.

https://learn.sparkfun.com/tutorials/capacitors/

I'm at work but can draw an example of what I mean later if it doesn't make sense. Just trying to simplify the math and concepts for people just learning.

If you jumper across the blown bulb, the measurement would be 0, but if you leave the circuit broken where the bulb was and measure there, as in your latest diagram, the answer is not 0.

EDIT: Changed the wording for clarity.

That's a much more complicated answer.

If you touched where you have the multimeter in your latest graphic, you would not have to bear the full 18.9 volts. Your body would act as a resistor in the circuit, it's easy to model if you make some assumptions about what that resistance value is. The 2 working lamps would bear some of the load as well.

Even though a multimeter at that point would measure 18.9 volts, once you completed the circuit with your body there would be a voltage drop across the bulbs. According to Kirchoff's voltage law, the voltage drop across those three elements (bulb, body, bulb) would have to total 18.9 volts.

Ampere rating on a power supply is how much it *could* supply, not what it tries to push out.

You could have a 6.3V 100 Amp supply and it would work fine on your bulbs.

However, there are constant current power supplies (like for LEDs) that will change their voltage to make sure the current stays at a constant level.

Maybe make the background color of the "approved" ones a different color, so people can quickly scroll and visually catch one of the approved ones passing by.

New version of the EE bible came out last month:

http://www.amazon.com/Art-Electronics-Paul-Horowitz/dp/0521809266/ref=sr_1_1

Hah, I still have that book too. That really brings back some memories. I have a bunch of the smaller Mims books they used to have too. Still up in my dad's attic I think, I'll have to dig those up next time I'm there.

Hahahaha, best post today.

It's all physics.

That's one thing I love about being an engineer. So much of the math and concepts are shared by all the STEM subjects.

Haha, I totally feel you on being bored while learning it. I always thought "We have computers now, why do I care about how to integrate something by hand?"

Turns out I was even stupider then than I am now. Not a week goes by that I don't heavily lean on the many years of math I took. I'm not even in the electronics industry these days, lol.