1. Electricity: Designing Circuits
Based upon Engineering is Elementary
An Alarming Idea: Designing Alarm Circuits

2. Teacher Tips
The most common reasons that buzzers and lights bulbs not working:
The clips on the jumper cables are not connected fully.
The red and black wires on the buzzer are connected opposite the way they need to be.
The bulb is not screwed in all the way.

3. Materials for Circuits
D-cell batteries
D-cell battery holders
light bulbs
light bulb holders
knife switches
buzzers
jumper cables (wires with alligator clips on each end)

4. Simple Circuit Trouble shoot (if light bulb does not light)
Is battery charged?
Is light bulb in place (touching base plate of light bulb holder)?
Is light bulb burnt out?
Are jumper cables attached to metal parts of light bulb holder and battery holder?
Are jumper cables working correctly?
Is your circuit closed?

5. Use the schematic below to create a series circuit with a switch

6. This is what it looks like when the circuit is closed

7. This is what it looks like when the circuit is open

8. Following this schematic, create a series circuit

9. This is the circuit – 1 switch open

10. This is the circuit – closed

11. Following this schematic, create a parallel circuit

12. What happens when you open one switch?
This image shows both knife switches closed. When you open one the light bulb on the right is not lit.

13. Build this circuit with a buzzer
Make sure the red wire is connected to positive and the black wire is connected to the negative battery terminal.

14. This is what it should look like
Note the batteries are reversed, so the wires on the buzzer are switched. One common problem with the buzzer not sounding is wrong polarity of battery supply with respect to the buzzer. The buzzer has a transistor inside and transistor will pass current if correctly aligned, else the current will not flow if incorrectly aligned.

15. Will the light bulb light? Why or why not?1 2
1. Yes No – needs a battery No – the wire has a gap Yes 3 4