Why do computers need to be cooled?
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For anything to ever occur, energy must be transferred. When energy is transferred heat is always produced. Heat is a spectrum between cold and hot. The faster things move (the faster the energy transfer) the more particles move, the more particles move in confined spaces, the more hot they become due to the consistent energy transfer (energy movement). If not cooled, the things that make a computer a computer would overheat and malfunction.
Computers make a lot of heat when they run. This heat comes from the processor (also called CPU, central processing unit) and, if the computer has one, the graphics card (also called GPU, graphics processing unit).
The CPU and GPU are computer chips. They make a lot of heat because they have millions of little electrical devices inside them. Those electrical devices are called *transistors*.
If the heat is not removed from the CPU and/or GPU, then eventually those little transistors (and maybe other components) will start to get damaged over time. This will lead to the computer not working any more.
Because the electricity used to do the valuation gets converted to heat if they get too hot they will do stuff incorrectly and at an even higher temperature get destroyed.
If you use low-performance CPUs they can be passivity cooled by the surrounding air, cellphones do that but high-performance computers need an active system like fans to keep them cool. It is possible to a higher-performance computer passively too the problem is heat sinks will be impractically large, heavy, and expensive.
Your brain do the same thing, the energy that is used becomes heat. If you can get cooled down by the environment you will overheat and die.
Your body does use a way of active cooling. If you walk you on in general not get too warm. If you run you use more energy and produce more heat. The active cooling system we have is sweating, the water requires energy to evaporate and it cools us down.
Because electronics are made out of metal and plastic (and a few other types of material), and all of those things will stop working right if they get too hot (melting, burning, changing shape, losing their electrical properties, etc.). Because the electricity being used in computers creates enough heat for it to become “too hot”, the computer needs to be cooled in order to keep working for more than a few minutes.
Electronic stuff (like our body) is not 100% efficient at using it power and will create heat as a by product.
Now imagine you running but only having a hand size to cool you down. That may likely not end well without active cooling.
Computers are based off of microscopic transistors. Every time one of these transistors switches from one state to another, it generates a small amount of heat. Multiply this small amount of heat over billions of transistors switching billions of times every second, you wind up with an amount of heat that you need to actively manage, by means of heat sinks and fans.
The average electric space heater works by passing electricity through a resistive circuit. If the resistive circuit is in a little box, you probably have a fan blowing through that circuit, which cools it down by spreading the heat into the room using convection. You may have a heater where the fan keeps running a bit after you turn it off, which is meant to cool the circuit down to a safe temperature.
Why all this? Because a CPU is just an electric space heater that also does useful work. Heat is created due to resistance in the circuit just as above, conduction is used to move the heat to the heat sink, and convection is used to move it into the room. The only difference is that we tend to think of this heat as waste instead of the desired result. But you can heat your room in the Winter using a powerful computer, or several of them.
There are many computers that do not need to be cooled, e.g. in your washing machine, watch, clock, etc. Generally low end computers.
Mid and high end computers in phones, tablets, laptops and desktops need cooling, or thermal management, because they would otherwise become too warm (and stop to function or degrade). Transistors in a computer only work properly in a specific temperature range. Furthermore, the housing of a chip can melt. The goal, in general is to keep them below 60C or 100C.
The heat is created because with each bit that changes in a processor, and that is basically the job of a processor, we fill up or empty internal capacitors. Both actions cause current to flow which has some losses. The losses are converted into heat.
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