Key relationship
E=k P/d²; R=1 MΩ/[1+√(E/10 lux)].
Physics · Practical apparatus
LDR response to lamp power
Keep distance fixed while varying lamp power. The calibration converts lamp watts into illuminance at the sensor; the LDR converts illumination into nonlinear resistance. Compare this investigation with the distance experiment.
Open the interactive experiment →LDR response to lamp power
தொலைவை நிலையாக வைத்து விளக்குச் சக்தியை மாற்றவும். LDR மின்தடை ஒளிச்செறிவுடன் நேராக அல்லாமல் மாறும்.
Key notes, relationships and model limits
Practical tip
Keep distance fixed while varying lamp power. The calibration converts lamp watts into illuminance at the sensor; the LDR converts illumination into nonlinear resistance. Compare this investigation with the distance experiment.
Common trap
Different lamps can produce different illuminance at the same electrical wattage.
Model limits
Prescribed lamp illuminance efficiency and empirical LDR calibration. Electrical watts are not universally proportional to lux; spectral and temperature effects omitted.
What you will learn
Run a controlled virtual lamp-power investigation.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
k10 luxm²/W,P20 W,d1 m gives200 lux.
Why this matters
The model connects ldr response to lamp power with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
To isolate lamp-power dependence, keep which apparatus quantity fixed?
- Lamp power
- Distance
- All meter readings
Read the explanation
Distance otherwise changes illuminance independently.
Course connection: Virtual apparatus preparation. Check exact board/exam membership in the syllabus sources. Physical practical work remains necessary.