Smartphone

What is inside

• The sandwich. A phone is a stack of thin layers: glass, touch sensor, screen, a metal frame, the main board and battery, and a back cover.
• The screen. The touch layer feels your finger through the glass. The display beneath it makes every picture out of red, green and blue dots.
• The brain. One chip the size of your fingernail does the thinking, the drawing and the remembering, using billions of tiny switches.
• The battery. A lithium battery stores energy by moving tiny lithium ions from one plate to another. Charging pushes them back.
• The radios. Antennas turn your voice into radio waves and send them to a tower. Other antennas listen for Wi-Fi, Bluetooth and satellites.
• The senses. A tiny motion sensor knows which way is up, the camera catches light, the microphone and speaker turn sound into vibration and back.

Stories in this thing

• Seven layers in eight millimetres. Pull the phone apart, one sheet at a time
• A picture from three colours. Red, green and blue — and nothing else
• What happens when you tap. From your fingertip to the chip and back, in a blink
• Where the battery’s energy lives. Lithium ions, shuttling between two plates
• A call across India. Your voice, turned into numbers, waves and back
• How the phone knows which way is up. A speck on springs, a lens and a trembling sheet

School topics it covers

• Light & colour
• Electricity
• Sound & radio

How children use it

Pull it apart with one slider, tap any part to hear what it does, follow a short story read aloud, then answer a few questions. Every thing comes with experiments to try at home and study notes linked to the NCERT chapter it supports.

More things to open

• Family car — Follow one drop of petrol from the tank all the way to the wheels.
• Aeroplane — How 70 tonnes of metal takes off, cruises and lands.
• Cruise ship — Why steel floats — and the secret crew corridor inside.
• Electricity — From the power station to your switch — and what happens when you flick it.
• Humanoid robot — Motor muscles, camera eyes and a computer brain.
• Planet Earth — Cut it open to the core, crash India into Asia, erupt a volcano.