# Better Understanding Circuits (Week 9)

Hello everyone! Since I was not able to complete my full box, I thought I would spend this post brushing up on my circuitry knowledge – I’ve taken an ECE course here at UIUC before, but I feel like I’ve already forgotten all the little technical things you should know about a circuit.

Did you know that the LEDs used in class (and in many other places and in many other things in the world) were invented here at U of I? Light emitting diodes (LEDs) were invented by Professor Nick Holonyak Jr., a PhD student of Nobel Prize winner John Bardeen. Holonyak went on to produce the first version of the LED. There’s a UIUC-published article about him here. Put simply, LEDs use a p–n junction diode that will emit light when activated. I studied the p-n junction in one of my classes, but always thought it was a bit confusing to understand!

A circuit can be in series or parallel. What does this mean? In a series circuit,  the components (a resistor, for example) are connected along a single path. When you look at a drawing of a series circuit, you will see  that you can put your finger on a start point and essentially draw a box around the entire circuit, hitting each component along the way. A series picture can be found below. Try following it around with your finger!

Conversely, a parallel circuit’s components are connected along multiple paths. You can’t trace your finger around the entire circuit without taking a diversion. Look at the image below to understand exactly what I mean by that.

This video does a good job explaining the differences. It’s important to know the differences between series and parallel  because they are both used in real-life applications, from your twinkly lights to the switches in your house. You’ve seen how we used LEDs and knowing how parallel versus series worked as well as ensuring oppositely charged lines didn’t cross were key in ensuring the LEDs behind our embroidery pieces worked.

I hope everyone’s boxes turned out well and hope you all have a great spring break!