Lecture on Light Dependent Resistors (LDRs)

Objectives

• Recognize the symbol for a Light Dependent Resistor (LDR).
• Describe how the resistance of an LDR changes in light and dark conditions.
• Explain how LDRs can be used in circuits.

Introduction

• Light Dependent Resistor (LDR) is a type of resistor.
• Used to control potential difference in circuits.

Symbol for LDR

• Important to learn and recognize the symbol for LDR.

Characteristics of LDR

• Dark Conditions:
  • High resistance.
• Light Conditions:
  • Low resistance.
• Graphical Representation:
  • High resistance with low light intensity (dark).
  • Low resistance with high light intensity (light).

Applications of LDRs

Mobile Phones

• Used to turn off the screen when the phone is held to the ear (battery conservation).
• Circuit Explanation:
  • LDR in series with a lamp (mobile phone screen backlight).
  • Light Conditions:
    • Low resistance of LDR.
    • Low potential difference across LDR.
    • High potential difference across lamp, lighting up the screen.
  • Dark Conditions (phone to ear):
    • High resistance of LDR.
    • High potential difference across LDR.
    • Low potential difference across lamp, dimming the screen.

Garden Lamps

• Circuit designed to activate lights in darkness and deactivate in light.

Conclusion

• Be able to recognize and draw the LDR symbol.
• Understand resistance changes in different light conditions.
• Explain practical applications of LDRs in circuits.

• Additional Resources:
  • Revision workbook available for further questions and exercises on LDRs.

[Music] Note: This lecture was accompanied by music.