The two-state (on/off) system
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. A light switch is either off or on. Is this a two-state system?
2. In binary, which pair of digits is used to write the two states?
3. A light switch is off. Which digit shows this state?
4. A row of 4 lights is on, off, on, on. How is this written in binary?
5. Which of these is NOT a two-state system?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1off = 0, on = 1 | AA light switch only has two states, off and on, so it uses only 0 and 1. There is no state 2. | |
| 2light switch: 0 or 1 | BA light switch has only two states, so it can be shown with one binary digit. | |
| 3Three light switches in a row can show a binary pattern, where off is 0 and on is 1. | CThe usual rule is the other way round: off is 0 and on is 1. | |
| 4A binary bracelet uses two bead colours: one colour means 0 and the other means 1. | Doff on on = 011 | |
| 5A light switch has 3 states: 0, 1, 2 | EA two-state system written in binary: off is 0 and on is 1. | |
| 6off = 1, on = 0 (in the usual binary rule) | Fwhite = 0, black = 1: black white black = 101 |
C
Definitions
two-state system
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
light ← _ // the light is off
2.
bead ← _ // the bead is on
3.
IF switch = _ THEN
DISPLAY "Light is on"
END IF
4.
states ← _ // off and on
5.
switch ← ___ switch // flip the state
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
light = "off"
B
state = 2
C
if light == "on":
D
state = 1
E
print(state)
Question 2
A
switch = 1
B
if switch == 1:
C
print("light is off")
D
else:
E
print("light is off")
Question 3
A
states = ["off", "on"]
B
switch = 1
C
print(states[2])
Question 4
A
light = "on"
B
if light = "on":
C
bit = 1
D
else:
E
bit = 0
Question 5
A
states = ["off", "on", "dim"]
B
print(len(states))
C
# output: 2
Answer Key
The two-state (on/off) system
Section A: Quick Questions
Q1
A — Yes, it has only two possible conditions
Q2
A — 0 and 1
Q3
B — 0
Q4
B — 1011
Q5
A — A dimmer dial with 10 brightness levels
Section B: Match the Pairs
Q1
off = 0, on = 1 → A two-state system written in binary: off is 0 and on is 1.
Q2
light switch: 0 or 1 → A light switch has only two states, so it can be shown with one binary digit.
Q3
Three light switches in a row can show a binary pattern, where off is 0 and on is 1. → off on on = 011
Q4
A binary bracelet uses two bead colours: one colour means 0 and the other means 1. → white = 0, black = 1: black white black = 101
Q5
A light switch has 3 states: 0, 1, 2 → A light switch only has two states, off and on, so it uses only 0 and 1. There is no state 2.
Q6
off = 1, on = 0 (in the usual binary rule) → The usual rule is the other way round: off is 0 and on is 1.
Section C: Definitions
Q1
two-state system — A system with only two possible conditions, like a light switch being off or on. We write the two states as 0 and 1, which is the idea behind binary.Section D: Fill in the Blanks
Q1
light ← 0 // the light is offQ2
bead ← 1 // the bead is onQ3
IF switch = 1 THEN
DISPLAY "Light is on"
END IFQ4
states ← 2 // off and onQ5
switch ← NOT switch // flip the stateSection E: Spot the Error
Q1
B — A two-state system only has the values 0 and 1. Off is written as 0, so the line should be state = 0, not 2.
Q2
C — The value 1 means on. When switch == 1 the program should print "light is on", not "light is off".
Q3
C — A two-state list only has positions 0 (off) and 1 (on). Position 2 does not exist. It should be states[switch] or states[1].
Q4
B — A single = assigns a value. To check whether the light is on, use the comparison ==, so the line should be if light == "on":.
Q5
A — A two-state system has only two conditions. Adding "dim" makes three states, so the list should be just ["off", "on"].