Circuits that solve problems
Circuits that solve problems: alarms, doorbells, sensors and traffic lights. Read one part at a time and tap “I know this”. Then test yourself in the quiz.
Know it already? Jump straight to the quiz
Alarms and bells
A simple burglar alarm: when the window opens, it closes a switch and the buzzer sounds. A pressure switch under a doormat closes the circuit when someone steps on it. A rain alarm has two metal plates close together: rainwater conducts across the gap.
| Circuit | Problem it solves |
|---|---|
| Doorbell (cell, wires, push switch, buzzer) | Lets people know someone is at the door |
| Fridge light | Light only when the door is open |
| Seatbelt beep | Reminds people to buckle up |
| Lighthouse | Warns ships of rocks at night |
Sensors
- A street light with a light sensor switches on by itself when it gets dark.
- A solar street light: the panel charges the battery in the day for the night.
- A kettle switches itself off when the water boils: a thermostat (heat switch).
- A farmer wants to know when her tank is full: a float switch sets off a buzzer.
Problems and fixes
During load-shedding, traffic lights without backup power go off and the intersection becomes dangerous. Your alarm circuit does not work? Check the wire connections and the cell first. A small LED glows to show a device is on.
Remember this and test yourself
- A buzzer makes the warning sound in an alarm.
- A doorbell uses a push switch: it rings only while you press it.
- Sensors: light sensor (street lights), motion sensor (security light), thermostat (kettle), float switch (tank).
- Two safety switches that must both be closed: in series. Either of two windows is enough: in parallel.
- Traffic lights in South Africa: green → amber → red.
Write these points in your book. Read them again the night before the test.
Both must be closed? Series (“AND”). Any one is enough? Parallel (“OR”).
Important words
First say what the word means, then turn the card over.
Match column A to column B
Tap a word in column A, then its meaning in column B. You can also start in column B.
True or false?
Read the question and the answer. Is the answer right? Tap True or False.
Now the real quiz!
The quiz has many more questions on this topic. Every question shows straight away whether you are right and explains why.
Take the quiz: Circuits that solve problems- Read one part together and ask your child to tell it back in their own words.
- The ticks (“I know this”) are saved on this device only. We never ask for names or emails.
Follows CAPS for Grade 6 Natural Sciences and Technology. Always check your teacher’s notes and textbook too.