Simple LED Circuit
A circuit is a loop that allows electricity to flow. The flow of electricity is called current. Current is pushed through a circuit by differences in voltage.
The most important fact you need to know is this:
Current flows from higher voltage to lower voltage.
You may have heard the words “current” and “voltage” before. Perhaps you have seen the word “volts” printed onto batteries.
When an electrical circuit is connected to both ends of a battery, then current will flow through the circuit from the higher voltage end of the battery (indicated by +) to the lower voltage end (indicated by -).
It may help to think about current as a fluid that flows from positive to negative.
To understand this better, let’s study a simple component:
The red bulb-like component is called an LED, which is short for “Light Emitting Diode”. An LED will glow if a current passes through it. But LEDs are special, in that the current needs to flow only in one direction (into the long (+) leg and out of the short (-) leg) for it to work. Trying to force current into the short leg can blow up the LED. LEDs don’t like that.
So, can we just connect the long leg to the (+) side of a battery and the short leg to (-)? NO WAY!!! LEDs can get damaged if too much current flows through them. To decrease the amount of current that flows in a circuit, we use resistors. They look like this:
The colored stripes are a code that indicate the amount of resistance. Resistors with a larger value reduce current more than resistors with a smaller value.
Therefore, to make an LED glow, we must connect to it through a resistor to a battery. Since we can’t just hold these things in place, we’re going to use breadboards to make connections from component to component. Also, instead of batteries, we’ll use the power sources on the breadboards. That’s what the next page is all about!