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Power, cooling and the display

Understand how a computer gets its power, why heat matters, and what the numbers on a screen mean. You will learn how to look after a battery, keep a laptop cool and set up the display comfortably.

25 minbeginnerPractical task needs a laptop or desktop

Marking a lesson as read does not prove you can do it. Skills count as demonstrated when you pass the quiz (not yet) and complete the practical tasks (not yet).

By the end of this lesson you will be able to

  • Describe the path electricity takes from the wall socket to the parts of a laptop.
  • Give three habits that help a laptop battery last longer.
  • Explain why heat is a problem and how a laptop keeps itself cool.
  • Explain what resolution, refresh rate and brightness mean.
  • Say which symptoms point to a power, heat or display problem, and which fixes are safe for a beginner.

Power, heat and the screen account for a large share of everyday laptop trouble: a laptop that will not charge, that gets too hot to touch, or a screen that is dim or blurry. These parts are also where beginners can do harm by trying clever fixes. This lesson explains how each works so you can look after them well and know when to stop and ask for help.

How power reaches the parts

The electricity from your wall socket is called mains power. It is high voltage and dangerous, and a computer's chips need much lower, steady voltages. The power supply converts one into the other. On a laptop, this is mostly the charger brick, with more circuits inside the laptop. On a desktop it is a metal box inside the case.

A laptop also holds a lithium-ion battery. When the charger is plugged in, power goes to the laptop's parts and tops up the battery. When it is unplugged, the battery supplies the parts alone. A flat battery plus no charger means the laptop will not start.

Diagram

The path of electricity from the wall to the laptop's parts.

  1. Step 1: Wall socketMains power: high voltage
  2. Step 2: ChargerConverts to low, safe voltage
  3. Step 3: Power circuitsInside the laptop
  4. Step 4: BatteryCharges, or supplies power when unplugged
  5. Step 5: PartsProcessor, screen, storage
The path of electricity from the wall to the laptop's parts.
Read this figure as text

A flow of steps from the wall socket through the charger to the laptop's power circuits, with the battery and the parts.

Step 1: the wall socket supplies mains power, which is dangerous and high voltage. Step 2: the charger (power supply) converts it to a low, safe voltage. Step 3: the laptop's power circuits share that power. Step 4: the battery is topped up when the charger is connected, and supplies the parts when it is not. Step 5: the processor, screen and other parts run on the low voltage.

Looking after a battery

Every battery loses capacity slowly as it ages, and no habit stops that completely. A few habits slow it down. Heat is the main enemy, so do not leave a laptop in a hot car or on a sunny windowsill. Use the charger that came with the laptop, or one that your maker lists as suitable. Avoid letting the battery run to zero again and again. Many modern laptops also have a setting that limits charging to around 80 per cent, which helps if the laptop is plugged in most of the time. Look in Settings for such an option; the name and place differ by make.

Why heat matters

Electricity passing through chips makes heat, just as a bulb warms up. Too much heat damages parts and shortens their life. So processors have a way to protect themselves. A Heatsink draws heat from the chip, and a cooling fan pushes air across it and out of the vents. If cooling is not enough, the processor steps down its speed to cool off. This is called thermal throttling, and it is why a hot laptop feels slow.

Diagram

How a laptop moves heat out of the case.

  1. Step 1: Processor worksIt produces heat
  2. Step 2: HeatsinkDraws heat off the chip
  3. Step 3: FanBlows air across the fins
  4. Step 4: VentsWarm air leaves the case
How a laptop moves heat out of the case.
Read this figure as text

A flow showing the processor producing heat, the heatsink drawing it away, the fan pushing air, and warm air leaving through the vents.

Step 1: the processor works and produces heat. Step 2: the heatsink, a metal block with fins, draws the heat off the chip. Step 3: the fan blows cool air from outside across the fins. Step 4: warm air leaves through the ventilation slots on the side or back. If the vents are blocked, for example on a soft bed or a lap, the heat has nowhere to go, the fan runs loudly and the processor slows down.

  • Use a laptop on a hard, flat surface, not on a bed, sofa or blanket.
  • Keep the vents clear. On many laptops the vents are underneath, so a table is better than your lap.
  • Keep it out of direct sun and hot cars.
  • Dust builds up over the years and blocks the fan. A gentle blow of dry air across the outside vents is fine, but opening the laptop to clean it is for a technician.
Diagram

Working out what to do when a laptop gets very hot.

  • Is the laptop hot to touch and the fan loud?
    • YesIs it on a soft surface, or are the vents blocked?
      • YesDo thisMove it to a hard, flat surface, clear the vents and let it cool.
      • NoIs it still hot with nothing demanding running?
        • YesDo thisSave your work, shut down, unplug it and ask a technician. Do not open it yourself.
        • NoDo thisClose programs you do not need and wait a few minutes. Heavy programs make heat.
    • NoDo thisWarm is normal when the laptop is working. No action needed.
Working out what to do when a laptop gets very hot.
Read this figure as text

A decision tree for a hot laptop with advice about surfaces, closing programs and when to ask for help.

Start: is the laptop hot and the fan loud? If no, no action needed. If yes: is it on a soft surface or are the vents blocked? If yes, move it to a hard flat surface, clear the vents and let it cool. If no: close programs that you do not need and wait a few minutes. If it is still hot with nothing running, or it smells of burning, save your work, shut it down, unplug it and ask a technician.

The display

A screen is a display panel: a grid of pixels that light up in colours. The two most common panel kinds are LCD, where a light behind the panel shines through coloured filters, and OLED, where each pixel makes its own light. OLED can show deeper blacks; LCD panels are common and cheaper. Either is fine for learning.

Three numbers describe how a screen behaves. Resolution is the number of pixels across and down, for example 1920 by 1080. More pixels give finer detail. Refresh rate is how many times per second the screen redraws, measured in hertz (Hz); 60 Hz is standard. Brightness is how much light the screen gives out. You change brightness yourself, and the Resolution and refresh rate are normally best left at the settings the system recommends.

Diagram

Reading a typical screen specification.

1920Pixels acrosswidth
x by
1080Pixels downheight
,
60 HzRedraws per secondrefresh rate
Reading a typical screen specification.
Read this figure as text

The string 1920 by 1080 at 60 hertz split into width, height and refresh rate.

A typical display setting reads 1920 x 1080, 60 Hz. The first number, 1920, is the number of pixels across the screen. The second number, 1080, is the number of pixels down the screen. Together they are the resolution, called Full HD, about two million pixels. The last number, 60 Hz, is the refresh rate: the screen redraws 60 times each second.

Diagram

Two common kinds of display panel compared.

LCDBacklit panel
  • A light behind coloured filters
  • Common and cheaper
  • Blacks look slightly grey

Fine for everyday work.

OLEDSelf-lit pixels
  • Each pixel makes its own light
  • Deep blacks, strong contrast
  • Usually more expensive

Lovely, but not essential.

Two common kinds of display panel compared.
Read this figure as text

Two columns comparing LCD and OLED screens on how they make light and where they are used.

LCD: a light behind the panel shines through coloured filters; very common and usually cheaper; blacks look slightly grey in a dark room. OLED: each pixel produces its own light; deeper blacks and strong contrast; usually more expensive; used in many phones and some laptops. Both are good for everyday work; neither is better for learning.

Look at your display settings

Look, but leave resolution and refresh rate at their recommended values unless you know why you are changing them.

On Ubuntu 24.04

  1. Step 1: Open Displays

    Open Settings, then choose Displays in the left-hand list.

    You should see: You should see your screen, with Resolution, Refresh Rate and Scale options.

  2. Step 2: Read the values

    Note the current resolution and refresh rate. Do not change them for now.

  3. Step 3: Try brightness

    Open the system menu at the top right of the screen and move the brightness slider, then put it back at a comfortable level.

Common mistakes

  • ✖ Instead of: Leaving the laptop on a pillow or bed while it works hard.

    ✔ Do this: Use a hard, flat surface so the vents can breathe. Heat slows the laptop and shortens its life.

  • ✖ Instead of: Using the first cheap charger found online because the plug fits.

    ✔ Do this: A plug that fits is not enough. Match the voltage and use the maker's charger or a reputable replacement.

  • ✖ Instead of: Setting the resolution to the highest value because bigger sounds better.

    ✔ Do this: Screens look sharpest at their native, recommended resolution. A different setting can look blurry.

If something goes wrong

The laptop does not charge, but the charger plugged in earlier.
Try another socket, check the cable for damage and that the plug is fully in. Look for dust in the charging port and remove only what you can see with a dry wooden or plastic toothpick, with the laptop off and unplugged. If nothing works, ask a technician.
The fan is very loud and the laptop is hot.
Move to a hard flat surface and close demanding programs. If it stays loud with nothing running, the vents may be clogged with dust. Shut it down and ask a technician to clean it.
The screen is too dim to see.
Press the brightness key or use the brightness slider in the system menu or Settings. Some laptops dim on battery to save power; check the power or battery settings.
The picture looks blurry or too large.
Open the display settings and choose the resolution marked Recommended (Windows) or the highest listed one that matches your screen shape (Ubuntu). Use scaling instead of a lower resolution if text is too small.

Key terms

Power supply
The part that changes the electricity from the wall into the lower, steady voltages that the computer needs.
Lithium-ion battery
The rechargeable battery type used in nearly all laptops and phones.
Cooling fan
A small fan that moves air over hot parts and out of the computer.
Thermal throttling
When a processor deliberately slows itself down to avoid getting too hot.
Resolution
The number of pixels a screen shows across and down. More pixels means finer detail.
Display panel
The flat screen itself, made of a grid of pixels that light up with colour.

Practise it for real

Reading is not the same as being able to do it. Complete these on your own computer, then tick only what you have actually done. These ticks are your own honest record: nothing checks them for you.

Guided exerciseNeeds a laptop or desktop

Survey your laptop's power, cooling and screen

With your own laptop: (1) Find the charger and read the small print on it; note the voltage and the maker. (2) Find the ventilation slots on the laptop's sides or underneath, and check that nothing blocks them. (3) Open the display settings and note the resolution and refresh rate. (4) Adjust the brightness up and down, then set it to a comfortable level.

You have succeeded when:
Independent challenge

Challenge: write your battery and heat habits

Write five short rules for looking after your laptop's battery and keeping it cool, based on this lesson, in your own words. Then look at where and how you usually use your laptop, and mark any rule you break today. Choose one to change this week.

You have succeeded when:

Knowledge check

6 questions. You need 80% to pass. Mistakes here are part of learning, and you can retry as often as you like.

  1. Question 1.Put these in the order that electricity passes through them when a laptop is charging.
    1. Battery and the parts
    2. Charger (power supply)
    3. Laptop's power circuits
    4. Wall socket
  2. Question 2.A laptop on a soft duvet gets hot and slow. What is the most likely reason?
  3. Question 3.If a laptop battery has swollen so that the base bulges, you should keep using it carefully until it stops working.
  4. Question 4.Match each term to its meaning.
  5. Question 5.Amina's laptop will not charge. The charger's light is off, and a different socket also gives nothing. Her friend suggests prying open the laptop to check the battery.What is the most sensible first step?
  6. Question 6.A display setting reads 1920 x 1080, 60 Hz. What does 60 Hz mean?

Summary

  • The charger turns dangerous mains power into a safe low voltage; the battery tops up and supplies the laptop when unplugged.
  • Heat is the enemy of batteries and chips. Use a hard flat surface and keep vents clear.
  • A swollen battery, burning smell or very hot case means stop, unplug and ask for help.
  • Resolution is pixels across and down; refresh rate is redraws per second; brightness is yours to adjust.
  • Use the maker's charger and leave resolution at the recommended value.

Checklist: can you do these?

Marking a lesson as read does not prove you can do it. Skills count as demonstrated when you pass the quiz (not yet) and complete the practical tasks (not yet).

Related lessons

References and further reading

Official sources for details that can change between versions.

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