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# When its bright does an LDR have a high or low resistance?

Updated: 8/11/2023

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Q: When its bright does an LDR have a high or low resistance?
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### What is the principle of operation of LDR?

Working of light dependent resistor This circuit explains the principle of operation of LDR (light dependence resistor). The circuit has various applications like shadow alarm, automatic night/morning lamp. LDR, an acronym for light dependent resistor is a resistor whose resistance is dependent on light. The resistance of LDR is of the order of Mega Ohms in the absence of light and reduces to a few ohms in presence of light. In this circuit when the light falls on LDR, the resistance of LDR becomes low and the entire voltage drop takes place across the variable resistance VR1 (10K). As a result the base of transistor (T1) gets high input and it gets biased thereby glowing the LED. When no light falls on LDR, the resistance of LDR becomes high so almost entire voltage drop takes place across it and the base of transistor is at low potential. So transistor does not gets biased nor it becomes conducting, hence switching off the LED. The sensitivity of the circuit can be adjusted by varying the preset VR1. LDR, an acronym for light dependent resistor is a resistor whose resistance is dependent on light. The resistance of LDR is of the order of Mega Ohms in the absence of light and reduces to a few ohms in presence of light. In this circuit when the light falls on LDR, the resistance of LDR becomes low and the entire voltage drop takes place across the variable resistance VR1 (10K). As a result the base of transistor (T1) gets high input and it gets biased thereby glowing the LED. When no light falls on LDR, the resistance of LDR becomes high so almost entire voltage drop takes place across it and the base of transistor is at low potential. So transistor does not gets biased nor it becomes conducting, hence switching off the LED. The sensitivity of the circuit can be adjusted by varying the preset VR1.

### How do you measure light intencity?

Measure Light Intensity using Light Dependent Resistor (LDR) The resistance of the Light Dependent Resistor (LDR) varies according to the amount of light that falls on it. The relationship between the resistance RL and light intensity Lux for a typical LDR is RL = 500 / Lux Kohm With the LDR connected to 5V through a 3.3K resistor, the output voltage of the LDR is Vo = 5*RL / (RL+3.3) Reworking the equation, we obtain the light intensity Lux = (2500/Vo - 500)/3.3 For a low cost LDR, at the same light intensity, the part to part variation in resistance can be as high as 50%. Therefore such a low cost LDR is seldom used for measuring light intensity but more for light presence/absence detection.

### Is graphite a high resistance or low resistance of electricity?

Graphite is low resistance of electricity...

### Good conductors have a high resistance or low?

Good conductors have low resistance. A low resistance allows for the easy flow of electric current through the material. Materials like metals are good conductors because they have many free electrons that can move easily in response to an electric field.

### Which has the thickest filament - a high-resistance or a low-resistance bulb?

A low resistance bulb has a thicker filament.

### What is ment by high resistance and low resistance on a meter?

On a multimeter, a high resistance would indicate a high Ohmic value and a low resistance would indicate a low Ohmic value. Specific values would be relative to device you are measuring.

### Do meters usually have a high or low internal resistance?

It depends on the application. Voltmeters have a high internal resistance, while ammeters have a low internal resistance.

### What is high resistance and low resistance?

Low resistance lets electrons through easy, and high makes it harder for them to pass. Basically electricity is harder to flow through high resistance and vice versa.

### What is high resistance what is low resistance?

Low resistance lets electrons through easy, and high makes it harder for them to pass. Basically electricity is harder to flow through high resistance and vice versa.

### What wire connection better high or low resistance?

Usually low resistance is better.

### If a multimeter reads zero on the ohm scale is this high or low resistance?

zero is low resistance

### How can you get low viscoSity and high resistance?

You get low viscosity with thin liquids like water that flow easily. Low viscosity means the liquid has low resistance. You get high resistance when you have liquids that flow slowly like honey and syrup, which means high viscosity.