Why do computers need power supplies?

[AstroBenny]

I know very little about electricity...

Why do computers need a power supply? Why can't they just use power from the wall?

What are they actually doing?

[GreezyJeezy]

The power supply takes the 100 whatever volts from the wall and turns it to what your pic needs, if you used sting wall person will RIP PC.

the CPU useless like 1.2 volts and if you gave it 120 or whatever RIP

[GlassBomb]

1 minute ago, AstroBenny said:

I know very little about electricity...

Why do computers need a power supply? Why can't they just use power from the wall?

What are they actually doing?

It's converting to more usable voltages. 110/220v down to +3.3V, +5V, +12V and -12V.

 

And of course converting it from the AC that comes from the wall, to DC.

[ThinkWithPortals]

6 minutes ago, AstroBenny said:

I know very little about electricity...

Why do computers need a power supply? Why can't they just use power from the wall?

What are they actually doing?

If you ran the full amount of voltage from a socket through a PC it would explode.

Maybe. Probably not. You get my point.

Anyway, a PSU converts the massive voltages from the wall into much smaller, more manageable voltages and distributes them around the system.

Case in point: a socket outputs upwards of 100v. If you ran 100v through your CPU you'd kill it, it only uses about 1v

[Darel321]

9 minutes ago, AstroBenny said:

I know very little about electricity...

Why do computers need a power supply? Why can't they just use power from the wall?

What are they actually doing?

almost everything has some sort of power suply inside.. tv, radio, washing machine etc... there's not many things that actually run on 120v or 220v AC.. most things run on 12v DC.. we have 120 or 220v ac in the walls because its easier to distribute the power on longer distances without power loss

[v-raze]

48 minutes ago, AstroBenny said:

I know very little about electricity...

Why do computers need a power supply? Why can't they just use power from the wall?

What are they actually doing?

As others have said, it takes the high voltage from the wall and steps it down to usable levels.

 

There's a bit more to it than that though- the power from your wall is what's known as "AC" or Alternating Current. This is one of the two ways electricity is transferred, and as the title implies, it has a rapidly fluctuating alternation in current. This is why you may sometimes hear people talking about the frequency of the power coming from an outlet- this is the frequency at which the current alternates. Alternating current is ideal for moving a lot of electricity over a long distance with minimal losses.

 

Alternating current is less useful for powering actual devices. While lights, large appliances, and machinery can run off AC voltage, most consumer appliances and digital electronics rely on "DC" or Direct Current. Direct current is easier to store and use at smaller power levels. Computers and other digital devices need DC power because they need to apply a lot of small voltages with a high degree of precision, something AC power is not ideal for.

 

Your power supply is the middle man. It takes the AC voltage from the wall, and 'rectifies' it to DC voltage. It also provides several different levels of power for different parts of the system- these are 12v, 5v, and 3.5v outputs and are supplied to the different components as needed.

 

As @Darel321 mentioned, there are a lot of things that actually use DC voltage. Many of these have their power supplies built in, or use a small enough power supply that it is part of the cord, like a laptop. A lot of devices use 'wall wart' power supplies- these are the power cords that plug into the wall and have a large black box right at the plug. Inside that box is a small power supply of sorts that converts the AC voltage from the wall to a specific amount of DC voltage.

 

This is an oversimplification of it, but it should give you a basic understanding of the reason for a power supply. If you want to know more, there's a wealth of information available online. I linked a couple of wikipedia articles in the above text- if you find those too complicated, you can look at the simple english wikipedia articles for Direct Current and Alternating Current.

 

I hope I was able to answer your question satisfactorily, go ahead and message or reply to me if you still need help!