← ACARA Digital Technologies Years 7–8

Battery life and portability in a device

Faster hardware uses more power and adds heat and weight, so a laptop or phone gives up battery life and portability to gain speed.

Part of: ACARA Digital Technologies Years 7–8 — Hardware and Performance — Module 37

Understanding Battery life and portability in a device in ACARA Digital Technologies Years 7–8

What it does: Faster parts use more power, which becomes heat, so fans must work harder and make more noise. Extra performance adds weight and power use, so the battery runs out sooner and it is harder to carry. Gaining speed usually costs battery life and portability. It does not make the battery last longer. A light laptop saves power and weight, so it suits carrying around and long days away from a charger. A thin body cannot hold large cooling systems, so makers choose lower-power parts. This is another trade-off. This ignores the trade-off: a light device gains portability but gives up performance.

Common mistakes: A light laptop has a low weight. 1.2 is not greater than 1.5, so the message would never show. The test should be weight < 1.5. Faster hardware makes more heat, so the fans must spin harder and get louder. The line should be fanNoise ← loud.

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This module's key terms are also in a printable crossword (Modules 13–40) and word search (Modules 13–68).

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Learning
Duo
A gaming laptop has a powerful CPU and GPU. Compared with a light laptop, what is most likely?
Shorter battery life and more weightLonger battery life and less weight
Matches
The fastest laptop will always have the longest battery life.
↓
Faster hardware uses more power, so it usually drains the battery sooner. Speed and battery life are a trade-off.
Applying
Meanings
Term
performance trade-off
Meaning
Faster hardware uses more power and adds heat and weight, so a laptop or phone gives up battery life and portability to gain speed.
Practice
Light laptop: 12 hours battery, 1.2 kg, quiet fan
Testing
Gaps
batteryHours = batteryWh powerWatts
Check Answer
Spots
1weight ← 1.2
2if weight > 1.5:

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Quick Questions

1. A gaming laptop has a powerful CPU and GPU. Compared with a light laptop, what is most likely?
A. Longer battery life and less weight
B. Shorter battery life and more weight ✓
Faster hardware draws more power and needs bigger batteries and cooling, so speed is traded off against battery life and portability.
2. Which statement describes the performance trade-off?
A. Faster hardware usually uses more power, heat and weight ✓
B. Faster hardware always makes a battery last longer
Gaining speed usually costs battery life and portability. It does not make the battery last longer.
3. Which laptop is the better choice for a student who carries it to school all day and needs 12 hours of battery?
A. A light laptop with an efficient CPU ✓
B. A heavy gaming laptop with a powerful GPU
A light laptop saves power and weight, so it suits carrying around and long days away from a charger.
4. A laptop's battery is rated at 10 hours. Why might it last only 3 hours while playing a 3D game?
A. The CPU and GPU work harder and use much more power ✓
B. The battery shrinks whenever a game is opened
Heavy tasks make the parts draw more power, so the battery drains faster than the rated hours, which are usually for light use.
5. Why do gaming laptops often have loud fans?
A. Fans are added to make the screen brighter
B. Powerful parts make more heat that the fans must remove ✓
More performance creates more heat. Fans move the heat out, and faster fans make more noise.

Match the Pairs

performance trade-off → Faster hardware uses more power and adds heat and weight, so a laptop or phone gives up battery life and portability to gain speed.
battery life: 12 hours (light laptop) → A light laptop uses a low-power CPU and a small battery, so it lasts a long time and is easy to carry but is slower at heavy tasks.
A gaming laptop has a powerful CPU and GPU, so it gets hot and needs loud fans to cool down. → gaming laptop: heat = high, fan noise = loud
A gaming laptop has a big battery and heavy parts, so it is less portable and its battery drains fast. → gaming laptop: weight = 2.8 kg, battery = 4 hours
The fastest laptop will always have the longest battery life. → Faster hardware uses more power, so it usually drains the battery sooner. Speed and battery life are a trade-off.
A thin, light laptop is best for editing 4K video because it is easy to carry. → Portability does not give power. Light laptops use low-power parts that struggle with heavy tasks like video editing.

Key Term

performance trade-off
Faster hardware uses more power and adds heat and weight, so a laptop or phone gives up battery life and portability to gain speed.

Fill in the Blanks

1. batteryHours = batteryWh / powerWatts
Hint: Type the operator that divides stored energy by power use to give hours of battery life.
2. IF cpuTemp > 80 THEN fanSpeed = "high"
Hint: Type the keyword that starts the action to run when the heat condition is true.
3. portable = weightKg < 1.5
Hint: Type the comparison operator that checks the laptop weighs less than the limit.
4. totalWatts = cpuWatts + gpuWatts
Hint: Type the operator that adds the power drawn by both parts, as in a gaming laptop.
5. IF batteryHours < 3 THEN show("Plug in")
Hint: Type the variable name that holds how many hours of charge are left.

Spot the Error

Question 1
A weight ← 1.2
B if weight > 1.5:
C say("Light and portable")
Line B — A light laptop has a low weight. 1.2 is not greater than 1.5, so the message would never show. The test should be weight < 1.5.
Question 2
A cpuPower ← high
B heat ← high
C fanNoise ← quiet
Line C — Faster hardware makes more heat, so the fans must spin harder and get louder. The line should be fanNoise ← loud.
Question 3
A batteryWh ← 50
B powerUseW ← 10
C hours ← batteryWh * powerUseW
Line C — Battery life is the battery size divided by how much power the device uses. Multiplying gives a wrong answer. It should use /.
Question 4
A lightW ← 8
B gamingW ← 40
C if gamingW > lightW:
D say("Gaming lasts longer")
Line D — The gaming laptop uses more power (40 W vs 8 W), so its battery drains faster, not slower. The message should say it drains faster.
Question 5
A weight ← 2.5
B batteryHours ← 4
C if weight > 2:
D type ← "light laptop"
Line D — A heavy device with a short battery life is a gaming laptop, not a light laptop. The type should be "gaming laptop".

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