What does an actuator do?

produces movement from a signal. Motors and valves are actuators.

Which printer uses toner powder and a rotating drum?

laser. The toner is fixed to the paper by heat.

Which printer sprays droplets of liquid ink?

inkjet. The ink comes out of tiny nozzles.

How does a 3D printer build an object?

by adding material one layer at a time. It is sometimes called additive manufacturing.

What does a DLP projector use to form the image?

millions of tiny tilting mirrors. Each mirror reflects light towards the lens or away from it.

In an LCD screen, what do the liquid crystals do?

block or let through light from a backlight. The light itself comes from behind, usually from LEDs.

Output devices · Cambridge IGCSE Computer Science (9

In plain words

An output device takes binary results from the computer and turns them into something a person can use or something that changes the world: a picture, a page, a sound, a movement.

7 things to know

An actuator turns a signal from a computer into movement: a motor, a valve or a pump, for example.
An inkjet printer sprays tiny droplets of liquid ink from nozzles onto the paper. It is cheap to buy and good for photographs, but slow, and the ink is expensive.
A laser printer uses a laser to draw the page as a pattern of static charge on a rotating drum. Powdered toner sticks to the charged areas, is transferred to the paper, and is fixed by heat. It is fast and cheap per page for large print runs.
A 3D printer builds a solid object by adding material one thin layer at a time, following a computer-aided design.
An LED screen is made of tiny light-emitting diodes that produce the light for each pixel. An LCD screen uses liquid crystals to block or let through light from a backlight.
An LCD projector passes light through LCD panels for red, green and blue and combines them. A DLP projector reflects light off a chip covered in millions of tiny mirrors that tilt towards or away from the lens.
A speaker turns an electrical signal into sound: the digital data is converted to an analogue signal, which makes a cone vibrate.

Worked example

An office needs to print 500 copies of a ten-page report every week. Which kind of printer should it use?

That is 5000 pages a week: a large amount.
A laser printer prints quickly and its cost per page is low. Its toner cartridges last for thousands of pages.
An inkjet printer would be slow, and its ink cartridges would need replacing often at a high cost.
A laser printer is the better choice.

Tips and tricks

Match the printer to the job. Large volumes of documents: laser. An occasional high-quality photograph: inkjet.
An actuator is the output device of a control system. It is how a computer makes something move.

6 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Output devices: 6 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

What does an actuator do?
- measures temperature
- produces movement from a signal (the answer)
- stores data
- displays an image
Motors and valves are actuators.
Which printer uses toner powder and a rotating drum?
- inkjet
- laser (the answer)
- 3D
- none of these
The toner is fixed to the paper by heat.
Which printer sprays droplets of liquid ink?
- inkjet (the answer)
- laser
- 3D
- DLP
The ink comes out of tiny nozzles.
How does a 3D printer build an object?
- by cutting it from a block
- by adding material one layer at a time (the answer)
- by folding paper
- by photographing it
It is sometimes called additive manufacturing.
What does a DLP projector use to form the image?
- liquid ink
- millions of tiny tilting mirrors (the answer)
- a rotating drum
- a grid of beams
Each mirror reflects light towards the lens or away from it.
In an LCD screen, what do the liquid crystals do?
- produce their own light
- block or let through light from a backlight (the answer)
- store the image
- detect touches
The light itself comes from behind, usually from LEDs.

6 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

2 questions, 6 marks. Write your answers on paper, then check them.

Output devices

Cambridge IGCSE Computer Science (9–1) 0984 · 6 marks · papermunch.org

Name ______________________________ Date ______________

Describe how a laser printer prints a page.[4]
Show answerHide answer
A laser draws the image of the page as static charge on a rotating drum. Toner powder sticks to the charged parts of the drum. The toner is transferred from the drum to the paper. Heat then fuses the toner to the paper.
I got this one
Describe how a 3D printer makes an object.[2]
Show answerHide answer
It follows a design made on a computer and builds the object by laying down material one thin layer at a time.
I got this one

Answers: Output devices

1. A laser draws the image of the page as static charge on a rotating drum. Toner powder sticks to the charged parts of the drum. The toner is transferred from the drum to the paper. Heat then fuses the toner to the paper.
2. It follows a design made on a computer and builds the object by laying down material one thin layer at a time.