Smartphone

You are designing a new mid-range smartphone. Customers want a thin and durable device, but phones are commonly replaced after 2–3 years even though they are almost entirely functional. You decide how to build it, how long to support it and what happens to it after years of use.

• Students compare the effect of materials, construction and servicing on a phone's lifetime.
• Students explain why software support and battery replacement often decide how long a phone is used.
• Students use E = P · t and calculate charging time including losses.
• Students distinguish the order of preference: repair and reuse are usually better than recycling.

1. 1

   MaterialsDecision

   What materials will you use for the frame, boards and battery?

2. 2

   ConstructionDecision

   How will the phone be assembled?

3. 3

   BatteryDecision

   How will the battery be replaced?

4. 4

   Software supportDecision

   How long will the manufacturer provide updates for the phone?

5. 5

   ChargingDecision

   How will the phone be charged?

6. 6

   Physics mini-task

   How long does a phone take to charge? You draw energy from the socket with input power P, but only part of it reaches the battery – the rest is lost as heat.

7. 7

   Service and spare partsDecision

   Will the display, camera and connector be replaceable?

8. 8

   Take-back and second lifeDecision

   What happens to the phone after several years of use?

Modular design

A device made of replaceable parts (display, battery, camera).

Refurbishing

Repairing and testing a used device so it can be sold again.

Software support

The period during which the manufacturer releases security and system updates.

Charging efficiency

The share of energy stored in the battery in the energy drawn from the socket.

Take-back

The manufacturer accepts used devices back for repair, refurbishing or recycling.

• E = P · tEnergy is the product of power and time. From it the charging time follows: t = E ÷ P.
• E = E_bat ÷ ηEnergy drawn from the socket at charging efficiency η. For 15 Wh and η = 0.85 this gives ≈ 17.6 Wh.
• 1 Wh = 3 600 JConversion between watt-hours and joules.

1. 5 min

   Introduction

   When did you last replace your phone? For what reason? The difference between a fault and obsolescence.

2. 20 min

   Work in the app

   Pairs go through eight steps including the physics mini-task about charging.

3. 10 min

   Discussion

   Compare results and use the discussion questions from the results screen.

Total 35 minutes. See the teacher guide for shorter and longer variants.

• Software support and a replaceable battery often decide how long a phone is actually used – more than its materials.
• Fast charging saves time, not energy; higher power usually means higher losses and more heat in the battery.
• Refurbishing and a second life use the whole device, so they are usually better than recycling it straight away.

• “Phones are replaced because they break.”

  In reality: Very often they are replaced because the battery fades or software updates stop, even though the device still works.

• “Wireless charging is the greener choice.”

  In reality: Part of the energy escapes as heat, so more must be drawn from the socket for the same charge.

• “Charging uses most of a phone’s impact.”

  In reality: Running a phone is not very energy-intensive; making it has a much bigger impact, which is why using it longer matters.

1. 1.Why do people replace phones even when they still work?
2. 2.Fast charging saves time but not energy. When is speed more important than efficiency?
3. 3.Is it better to repair, refurbish or recycle a phone? Rank the options and justify the order.

• Homework: time how long a real phone takes to charge and compare it with the ideal E ÷ P estimate.
• Interview a local repair shop: which repairs are most common and which parts are hard to get?
• Design a take-back campaign: how would you convince people to hand in an old phone instead of keeping it in a drawer?