Power Supply in Computers and Phones – JSS1 Computer Hardware & GSM Repair Lesson Note (Second Term)

Power supply is the way electricity is given to a computer or phone so that it can work.

Behavioural objectives

1. Define a battery, a charger, a UPS and a power bank.
2. Name the main power source and backup power for a phone, a laptop and a desktop computer.
3. Explain how a UPS protects a desktop computer when power fails.
4. State at least four safety rules for batteries, chargers and sockets.

What is a battery?

A battery is a device that stores electricity so that a phone or laptop can work without a wall socket.

• Mobile phone battery: most phones use a lithium-ion battery, which is light and can be recharged many times.
• Laptop battery: it is bigger than a phone battery because a laptop has a larger screen and a more powerful processor (the “brain”) to feed.
• CMOS battery: a small coin-shaped battery on the motherboard of a computer. It keeps the date, time and basic settings.

How should we care for a battery?

• Swelling: if a battery starts to swell (looks fat), stop using it at once. It can be dangerous.
• Repair: take a swollen battery to a trained repairer. Do not press it, open it or throw it in a fire.
• Heat: keep phones and laptops away from strong heat, because heat damages batteries.

What is a charger?

A charger is a device that changes high-voltage mains electricity into a small, safe amount that a phone or laptop can use to recharge its battery.

What are the parts of a phone charger?

• Adapter (the block): the square part that plugs into the wall socket. It steps the voltage down and changes the mains electricity into the form the device needs.
• USB cable: the cable that carries power from the adapter to the phone.

How does a charger work?

1. The adapter is plugged into the wall socket.
2. The adapter reduces the high voltage to a small, safe voltage.
3. The cable carries this power to the phone or laptop.
4. The power fills the battery with electricity.

What are the safety rules for chargers?

• Pulling out: never pull a charger out by the cable. Hold the plastic head.
• Damaged wires: do not use a charger with naked or torn wires. It can give you an electric shock.
• Sparks: if you see sparks when you plug in, tell an adult. The socket may be loose.

What is a UPS?

A UPS (Uninterruptible Power Supply) is a box with a battery inside that keeps a computer running for a short time when the mains power fails.

Why do we need a UPS?

• Sudden shutdown: when the lights go out, a desktop computer switches off at once.
• Lost work: unsaved schoolwork can be lost.
• Hardware damage: a sudden shutdown can harm the computer.

How does a UPS work?

1. Plug the computer into the UPS.
2. Plug the UPS into the wall socket.
3. The UPS charges its battery while the mains power is on.
4. When the power fails (people still say NEPA or PHCN goes off), the UPS takes over at once.
5. The UPS beeps to tell you the power is out.
6. Save your work and shut down the computer properly before the UPS battery runs out.

• Backup time: it is usually only a few minutes. It depends on the UPS and on what is connected to it.

What is a power bank?

A power bank is a portable battery used to recharge a phone when there is no wall socket.

• Use: it is useful when travelling or during a power cut.
• Safety: do not leave it in a hot car, because heat can damage it.

What power source does each device use?

Different devices use different main power sources and backup power.

• Desktop power supply unit: a desktop has a power supply unit inside the system unit. It changes mains electricity into the power the parts need.
• No main battery: a desktop has no battery to run it, so it switches off when the power fails. That is why it needs a UPS.

What are the best practices for power safety?

• Save often: click “Save” regularly, even with a UPS or a good battery.
• Keep air flowing: do not use a laptop on a soft pillow or bed for long. It blocks the air vents and makes the laptop and battery too hot.
• Check sockets: report loose or sparking sockets to an adult.
• Use good cables: replace damaged chargers.

Class discussion

1. Does a desktop computer have a battery inside it like a phone does?
   
   Answer: it has only a small CMOS battery for the clock and settings. Nothing powers the computer when the mains fails, so it needs a UPS.
2. Why is it wrong to use a laptop on a soft pillow for a long time?
   
   Answer: the pillow blocks the air vents, so the laptop and battery get too hot.
3. What should you do when your UPS starts beeping during a power failure?
   
   Answer: save your work and shut down the computer properly.

Evaluation

1. Define a UPS.
2. Name the two parts of a phone charger and state the job of each.
3. Give two signs or rules that show a battery or charger is unsafe to use.
4. State the main power source and the backup power of a laptop.

Assignment

Draw a table with three columns: device, main power source and backup power. Fill it in for a phone, a laptop and a desktop computer, then write two safety rules for chargers.