1. Daily Sprint START What is a capacitor? Draw its symbol.
Draw a circuit diagram for a camera flash.
What else could a capacitor be used for?

2. MSA Prep
Solve:
x = 4
y = 2
3x +4y +x2 - xy

3. Conclusion Questions
1.    Describe something other than the examples you’ve been given that you believe uses a capacitor and its function in the device. -

4. Conclusion Questions
2.    What do capacitors have to do with the dangers of older television sets?
- Older TV’s used large capacitors to operate. Those capacitors held enough charge to seriously injure someone if they touched it. The charge will remain in those capacitors long after the TV is out of use.

5. Transistors Transistors Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Transistors

6. Transistors Transistors Parts of the Transistor The First Transistor
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Transistors
Transistors
Parts of the Transistor
The First Transistor
Transistors as Amplifiers
Transistors as Switches
Night Light Circuit
This presentation is intended to be used with Activity Transistors

8. Symbol for Circuit Diagrams
Transistors
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Transistors
Transistor: A small electronic device used in a circuit as an amplifier or switch.
Symbol for Circuit Diagrams

9. Parts of the Transistor
Transistors
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Parts of the Transistor
BASE
EMITTER
COLLECTOR
The small base current controls the larger collector current.

10. Transistors
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
The First Transistor
Considered by some to be the greatest invention of the 20th century
Invented at Bell Laboratories in 1947
It is a crucial component in almost all modern electronic devices
Engineers are working toward making them smaller so that more can be placed on computer chips. Many today are already smaller than a human hair.
Replica

11. Transistors as Amplifiers
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Transistors as Amplifiers
Small load (input)
Large load (output)

12. Transistors
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics

13. Transistors as Switches
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Transistors as Switches
Large Current Load
Small Current Load
Build the circuit as shown.
When the switch is closed, you should notice that the LED in the circuit connected to the base is very dim.
But the other LED that is controlled is much brighter.
A small current amount switching on a larger current
Students may be able to build the following circuit without viewing the physical image.

14. Transistors
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Night Light Circuit
Challenge: Create a system with a light that comes on when it is dark, similar to a street light.
In the following circuit, will the LED be bright at day or night?
The LED will be bright during the day because brightness causes the photoresistor’s resistance to decrease.
When the resistance of the circuit decreases, more current can flow to the LED.

15. Transistors
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Night Light Circuit
In your engineering notebook, sketch the circuit shown below.
Current will always take the path of least resistance.
Use a highlighter to trace the path that current will take from the source.
Does current reach the base of the transistor?
Will current be able to reach the light?
The resistors in the circuit are added to protect the LED and the base of the transistor.
Current cannot reach the base of the transistor in order to cause current to flow through the transistor to activate the LED.

16. Transistors
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Night Light Circuit
In your engineering notebook, sketch the circuit shown below.
In brightness the photoresistor’s resistance is low.
Use a highlighter to trace the path when there is very little resistance from the photoresistor.
Does voltage reach the base of the transistor?
Will voltage be able to reach the light?
Current does not reach the base of the transistor, which does not allow current to flow to the LED.

17. Transistors
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Night Light Circuit
In your engineering notebook, sketch the circuit shown below.
In darkness the photoresistor’s resistance is high.
Use a highlighter to trace the path when there is a large amount of resistance from the photoresistor.
Trace the secondary path of resistance.
Is the voltage high enough to activate the base circuit of the transistor?
Will current be able to reach the light?
Once the resistance of the photoresistor becomes high enough, it will bypass that path, go through the base, switch on the transistor’s path, and light the LED.

18. Transistors
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Night Light Circuit
Build the circuit as shown to test using actual components using Snap Circuits® spring sockets.
If the circuit does not work as expected, troubleshoot using the flow chart provided in Activity Transistors (omit the suggestion to check solder connections).

19. Transistors
Gateway To Technology
Unit 6 – Lesson 6.2 – Electronics
Image Resources
Microsoft, Inc. (2009). Clip Art. Retrieved January 27, 2009, from