answersLogoWhite

0

light-dependent resistor, alternatively called an LDR, photoresistor, photoconductor, or photocell, is a variable resistor whose value decreases with increasing incident light intensity. An LDR is made of a high-resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron (and its hole partner) conduct electricity, thereby lowering resistance. A photoelectric device can be either intrinsic or extrinsic. In intrinsic devices, the only available electrons are in the valence band, and hence the photon must have enough energy to excite the electron across the entire bandgap. Extrinsic devices have impurities added, which have a ground state energy closer to the conduction band - since the electrons don't have as far to jump, lower energy photons (i.e. longer wavelengths and lower frequencies) are sufficient to trigger the device. Two of its earliest applications were as part of smoke and fire detection systems and camera light meters. Because cadmium sulfide cells are inexpensive and widely available, LDRs are still used in electronic devices that need light detection capability, such as security alarms, street lamps, and clock radios (Wikipedia 2005).

User Avatar

Wiki User

13y ago

What else can I help you with?

Related Questions

How do you set the sensitivity of a light dependent resistor?

using a variable resistor we can adjust the sensitivity of a light dependent resistor


Is Light dependent resistor an example of resistor?

yes, a variable resistor


What is an LDR symbol?

An LDR is a Light dependent resistor.


Who invented light dependent resistor?

K. K.


In technology what does LDR stand for?

LDR stands for Light Dependent Resistor. It is a type of resistor that changes its resistance based on the amount of light that falls on it. This change in resistance allows LDRs to be used in light-sensitive applications, such as automatic lighting controls.


What is the meaning of LDR?

LDR refers to Light Dependent Resistor.


What are the advantages and disadvantages of light dependent resistor?

itroduction on LDR


Who invented the light dependent resistor?

J.B. Gunn is credited with the invention of the light dependent resistor in the early 20th century. It was initially developed for military applications during World War II.


Materials required to study light dependent resistors?

a resistor , two multimeter ,


What is a light dependent resister?

As light falls on the conductor then emission of electrons would increase the conductivity and so its resistivity decreases. Such a conductor is known as light dependent resistor.


Where are light dependent resistors used for?

Its slows down energy when it passes thought the light depntent resistor.


What is a LDR dependent AC dimmer?

The LDR dependent AC dimmer is a Light Dependent Resistor which works by chopping off the parts of the AC voltage.