Hardware · 4 question types
Past paper frequency (2018 to 2024)
This topic accounts for approximately 3% of your exam marks.
Typically tested as 'give one use of…' or 'describe how this sensor works' questions.
There are three main touch-screen technologies. The key differences are how each one detects a touch.
| Feature | Resistive | Capacitive | Infrared |
|---|---|---|---|
| How it detects touch | Two flexible conductive layers that press together when touched, completing a circuit at the touch point | A grid of conductors holds a tiny electrical charge; the human body changes the charge when a finger gets close, and the screen detects the change | A grid of infrared light beams crosses the screen surface; a finger or stylus breaks the beams and the screen detects where |
| Works with... | Almost anything: fingers, gloves, plastic stylus, fingernails | Bare skin only (or specially-conductive styluses); standard gloves and non-conductive objects will not register | Almost anything that can block the light beam (finger, gloved hand, stylus) |
| Multi-touch? | No (or only basic) | Yes | Yes |
| Sensitivity / accuracy | Slow, less responsive | Fast, smooth, very responsive | Fast and very accurate |
| Screen quality | Image looks slightly dimmer (the touch layers reduce light through) | Sharp and bright | Sharp and bright |
| Wear / durability | Soft layer can be scratched or wear out | Glass surface; very durable | Frame can collect dust and dirt |
| Cost | Cheap | More expensive | Most expensive |
| Where you see it | Older smartphones, ATMs, point-of-sale terminals, industrial control panels where gloves are worn | Modern smartphones, tablets, touch monitors | Large interactive displays, kiosks, electronic whiteboards |