GoalDescribe how a sensor saves water or power and sketch an idea.
New words
sensor · a part that notices something, such as a hand, light, heat or smokeautomatic · working by itself, without a person pressing a switchsolar panel · a flat panel that turns sunlight into electricitypaper model · a drawing or cut-out that shows how an idea would work
Explanation
A sensor is like a pair of eyes for a machine. A sensor tap notices a hand under it and lets water flow. When the hand moves away, the sensor stops the water. Water flows only when it is needed, so none is wasted. A sensor lamp works in the same way: when a person is in the room the lamp is on, and when nobody is there it switches off. You can describe any sensor with an if-then rule: if a hand is under the tap, then water flows. Sensors have more jobs. They can help to set the temperature of a room, switch lights on and off in different ways, and detect smoke from a fire. A solar panel also helps to save resources, because it turns sunlight into electricity and can start work by itself when it is needed. Engineers plan an idea on paper first, so you can too.
a hand is under the tap→the sensor notices it→water flows→hand moves away: water stops
Worked examples
The sensor notices
Then
Saves or protects
the room is too warm
the fan switches on
comfort with little power
nobody is in the room
the lamp switches off
electricity
smoke in the air
the alarm sounds
people’s safety
This table shows three jobs of sensors in a home. Each sensor notices one thing and an action follows.
Salma’s class makes up a test with invented numbers. A normal tap stays open for ten minutes and uses 20 litres. A sensor tap used for the same job uses 6 litres. The sensor tap saves 14 litres in this made-up test.
person in the room→sensor notices→lamp on
Karim notices that the lamp in his classroom stays on during break when nobody is inside. He imagines a sensor above the door. If a person is in the room, then the lamp is on. If nobody is there, then the lamp is off.
Class activity
Choose one: clean the air in your room, or save electricity in your classroom. Draw the room on paper. Mark where the sensor would sit and draw an arrow to the part that acts. Write one sentence with “If … then …”. Make a small paper model if you like, and explain it to a family member. No device is needed.
Practice
1
What does a sensor tap do when you take your hand away?
It stops the water.
2
Which wastes less water: a tap that runs all the time or a sensor tap? Why?
The sensor tap, because water flows only when it is needed.
3
Which sensor job is shown by the alarm picture? Say the letter.
