← ACARA Digital Technologies Years 5–6

On and off switches in everyday things

A switch has two states. We write 0 for off and 1 for on, so a row of switches or LEDs can be written as binary digits, like 1 0 1 1.

Part of: ACARA Digital Technologies Years 5–6 — Representing Data with Numbers — Module 5, ACARA Digital Technologies Years 7–8 — Binary Number Representation — Module 2

Understanding On and off switches in everyday things in ACARA Digital Technologies Years 5–6

What it does: Each LED is written in order: on is 1, off is 0, so on-off-on-off becomes 1 0 1 0. Every switch is off, so each one is written as 0. We write 1 for on and 0 for off. Off is written as 0. A switch only has two states, so one binary digit is enough to describe it. Read left to right: on = 1, off = 0, on = 1, on = 1, so 1 0 1 1. There are three 0s (off) and one 1 (on). Any appliance switch that is off is written as 0.

Common mistakes: A switch has only two states, so the value must be 0 (off) or 1 (on). 2 is not a valid state. It should be light_switch = 1 or 0. The comment says the torch is off, and off is written as 0. The line should be torch = 0, not 1.

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Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

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This module's key terms are also in a printable crossword (Modules 44–57) and word search (Modules 44–71).

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Learning
Duo
A torch is switched on. Which digit shows this?
10
Matches
A torch that is switched on is written as 0
↓
0 means off, not on. A torch that is on should be written as 1.
Applying
Meanings
Term
0 = off, 1 = on
Meaning
A switch has two states. We write 0 for off and 1 for on, so a row of switches or LEDs can be written as binary digits, like 1 0 1 1.
Practice
off = 0
Testing
Gaps
IF torch = THEN
Check Answer
Spots
1# 0 = off, 1 = on
2light_switch = 2

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Quick Questions

1. A torch is switched on. Which digit shows this?
A. 1 ✓
B. 0
We write 1 for on and 0 for off.
2. A light switch is flipped down so the light is off. Which digit shows this?
A. 0 ✓
B. 1
Off is written as 0.
3. Which is the best reason a light switch can be written with 0 and 1?
A. It can have ten different settings
B. It has two states: off and on ✓
A switch only has two states, so one binary digit is enough to describe it.
4. A row of 4 LEDs is: on, off, on, on. How is it written?
A. 1 1 0 1
B. 1 0 1 1 ✓
Read left to right: on = 1, off = 0, on = 1, on = 1, so 1 0 1 1.
5. The row 0 1 0 0 means three LEDs are off and one is on. Is this true?
A. True ✓
B. False
There are three 0s (off) and one 1 (on).

Match the Pairs

0 → The switch, torch or LED is off
1 → The switch, torch or LED is on
A row of four LEDs where the first and third are on and the others are off → 1 0 1 0
Three light switches in a row that are all turned off → 0 0 0
A torch that is switched on is written as 0 → 0 means off, not on. A torch that is on should be written as 1.
LEDs: on, off, on, on written as 1 0 0 1 → The third LED is on, so it should be 1, not 0. The correct row is 1 0 1 1.

Key Term

0 = off, 1 = on
A switch has two states. We write 0 for off and 1 for on, so a row of switches or LEDs can be written as binary digits, like 1 0 1 1.

Fill in the Blanks

1. torch ← 1 IF torch = 1 THEN display "The torch is on"
Hint: Type the digit that stands for a switch being on.
2. lamp ← 0 display "The lamp is off"
Hint: Type the digit that stands for a switch being off.
3. // LED row: on, off, on, on LEDs ← [1, 0, 1, 1]
Hint: The second LED is off. Type the digit for off.
4. // kettle on, toaster off, fan on switches ← [1, 0, 1]
Hint: The fan is the last switch and it is on. Type its digit.
5. lightSwitch ← 0 lightSwitch ← 1 // someone flips the switch on
Hint: The switch was flipped from off to on. Type the new digit.

Spot the Error

Question 1
A # 0 = off, 1 = on
B light_switch = 2
C print(light_switch)
Line B — A switch has only two states, so the value must be 0 (off) or 1 (on). 2 is not a valid state. It should be light_switch = 1 or 0.
Question 2
A torch = 1
B print(torch)
C # The torch is off
Line A — The comment says the torch is off, and off is written as 0. The line should be torch = 0, not 1.
Question 3
A leds = [1, 0, 1, 1
B print(leds)
C # LEDs 1, 3 and 4 are on
Line A — The list is missing its closing square bracket. The row of LEDs should be written leds = [1, 0, 1, 1].
Question 4
A lamp = 1
B fan = 0
C print('lamp:' lamp)
Line C — There is a comma missing between the two things to print. It should be print('lamp:', lamp).
Question 5
A # The TV is off
B tv = 1
C print('TV', tv)
Line B — The comment says the TV is off, and off is 0. Writing 1 would mean the TV is on. It should be tv = 0.

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