Series. Parallel. Series-Parallel

      Here it is, what you have all been waiting for, my amazingly relevant, real-life electronics story.

Just recently I was over at my friends house and he was stringing Christmas lights in a fort that we made for his daughter when one half of the lights went out. Only one bulb was out. So why then did half of them turn off? What about the other half? What does this have to do with electronics? The answer, it has everything to do with electronics.

Series. Parallel. Series-parallel. These words describe how circuits are connected. After learning about Ohm’s Law and how voltage, current, and resistance interact, this is a great way to gain a deeper understanding in how current flows (Electron Flow that goes negative to positive. Don’t let all those textbooks fool you with conventional current that goes positive to negative. Spring that one on your teacher and watch them backtrack trying to explain why it’s like that.).

A series circuit has only one path to ground.

A series circuit has only one path for current to flow through. The current in a series circuit will remain the same throughout, while there will be voltage drops along each component. Therefor, the total resistance equals the resistances of all the resistors together or, R_t=R₁+R₂+R₃+… Think of a box, to complete a circuit it must follow the lines to get back to the beginning or starting point.

Imagine that the switch is another light. When the switch is closed, like it is right now, all the lights "light" up. When the switch is open, or in the up position, all the lights are off. 

Parallel circuit, similar to a ladder,
has multiple paths to ground.

On the other hand, a parallel circuit has more than one path for current to flow. The voltage across each path is the same in a parallel circuit while the current is reduced along each path. The math for a parallel circuit is slightly more complex, to find the total resistance you take the inverse of the all the resistor’s inverses added up. Inversely, it looks, and is, easier then it sounds. R_t=1/((1/R₁)+(1/R₂)+(1/R₃)+…). Simple. Right? Imagine a ladder where the current has many paths or rungs to take to complete the circuit.

Now to tie everything back together with the Christmas lights. When lights are placed in a series circuit, there is only one path for the current to travel down. When a singular light goes out, it acts like a switch, essentially breaking the path and not allowing the current to flow past it (Standing current) to the other lights. If one light does not get any current, then none of them do. A parallel circuit has multiple paths for current to travel down, so if a light were to go out, the current would still be able to flow through the other paths available and light the other bulbs.

Almost every mystery has been solved, save for one. Why did half of the strand go out when one bulb blew, and not the whole strand? Because it was a series-parallel strand of lights, there were two series strands attached to the same plug, meaning while one half is out, the other is still able to light up.

In a series-parallel circuit, if the light on the left was to go out, the two lights to the right would still be on because they still have a path to ground. If one of the lights on the right was out, both on lights on the right would be out because they are in series, while the light on the left would remain on.

...My mistake in "Player Piano" was my failure as a futurist. I did not foresee transistors, and so imagined that super computers would have to be huge, with bulky vacuum tubes taking up a lot of space. -Kurt Vonnegut in "Letters"