What affects the resistance of an LDR?
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What affects the resistance of an LDR?
Their resistance decreases as the light intensity increases: in the dark and at low light levels, the resistance of an LDR is high and little current can flow through it. in bright light, the resistance of an LDR is low and more current can flow through it.
How does the resistance of an LDR changes with light intensity?
The resistance of a LDR depends on light intensity. At low light levels, the LDR has a high resistance. As the light intensity increases, the resistance decreases. A LDR can be used as a sensor in cameras or automatic lights that come on when it gets dark.
What happens when resistance of LDR increases?
As this resistance increases in relation to the other Resistor, which has a fixed resistance, it causes the voltage dropped across the LDR to also increase. When this voltage is large enough (0.7V for a typical NPN Transistor), it will cause the Transistor to turn on.
What is the resistance of light dependent resistor LDR?
Light dependent resistor specifications
| Example Photoresistor Specifications | |
|---|---|
| Parameter | Example Figures |
| Max. resistance @ 10lux | 4.5kΩ |
| Typ. resistance @ 100lux | 0.7kΩ |
| Dark resistance after 1 sec | 0.03MΩ |
What is the relation of luminous intensity to resistance in LDR?
Resistance of an LDR is inversely proportional to the intensity of light that falls on LDR’s surface. In other words, with an increase in light intensity, the resistance of photoresistor or LDR decreases. And that’s why the graph between Resistance of LDR and intensity of light is hyperbolic in nature.
What is the resistance of the LDR when the potential difference across it is 4V answer?
At potential difference = 4V, current = 0.4, so Resistance = 4/0.4 = 10Ω
What happens to LED when LDR is exposed to light?
When the light level is low the resistance of the LDR is high. This prevents current from flowing to the base of the transistors. Consequently the LED does not light. However, when light shines onto the LDR its resistance falls and current flows into the base of the first transistor and then the second transistor.
Why does a resistor get hot GCSE?
So, when an electrical charge passes through a resistor, some of that electrical energy is transferred into heat, increasing the temperature. This extra energy causes the particles in the resistor to vibrate more.
What happens when an LDR is exposed to light?
When the light level is low the resistance of the LDR is high. This prevents current from flowing to the base of the transistors. However, when light shines onto the LDR its resistance falls and current flows into the base of the first transistor and then the second transistor.
What happens to the LED when the LDR is exposed to light?
When an LDR is exposed to a light of high intensity, the resistance value will decrease. It could drop from 1 MΩ to 2 kΩ. Circuit of a day/night switchnpn transistor is the control device, and an LED is the output device.
How does a light dependent resistor work?
Working Principle of LDR. These devices depend on the light, when light falls on the LDR then the resistance decreases, and increases in the dark. When a LDR is kept in the dark place, its resistance is high and, when the LDR is kept in the light its resistance will decrease.
What is the resistance of the light dependent resistor when the circuit is in the darkroom?
Characteristics of Photoresistor (LDR) When a light dependent resistor is kept in dark, its resistance is very high. This resistance is called as dark resistance. It can be as high as 1012 Ω and if the device is allowed to absorb light its resistance will be decreased drastically.