A photocell is made up of a semiconductor, the working of which is dependent on the intensity of incident light. When the amount of light exceeds a certain frequency, the electrons of the semiconductor are delocalized or "freed," and a photocell starts conducting. When the light is less, no electrons are freed, and the photocell doesn't conduct.Know More
The semiconductor that is used in a photocell is usually of a very high resistance. This allows the photocell to stop the flow of current completely when there is no light. When light falls on the photocell, it transmits energy into the semiconductor part of the cell. The frequency of incident light is directly proportional to the transferred energy, hence the more light, the more transmitted energy. When this energy exceeds a certain level, the electrons of the semiconductor are delocalized, and the photocell starts conducting. This is the reason why a photocell conducts electricity when a high intensity of light is subjected to it.
A common application of the photocell is the light-dependent resistor. LDRs are used commonly in light sensors, street lights and energy-efficient lighting solutions. A photocell also plays a very important part in efficiently using daylight by turning off lights when natural light reaches a normal level.Learn more about Measurements
Barometers measure air pressure to help predict the weather and to determine the altitude of an aircraft. Mercury barometers measure pressure as air presses on a cistern of mercury, changing the height of a column of the mercury that extends through a vacuum in a glass tube. Aneroid barometers measure direct air pressure on a flexible diaphragm and are less accurate than mercury barometers.Full Answer >
According to About.com, Albert Einstein started out working as a technical assistant examiner at the Swiss Patent Office in 1902. After his received his doctorate in 1905 and had several articles published, he began to rise as the scientist he is known as today. Starting in 1909, he accepted teaching positions at the University of Zurich, University of Prague and later the University of Berlin.Full Answer >
Blown fuses, low coolant levels, malfunctioning batteries and problems with wiring connections are all potential causes of a car's defroster not working. A defroster is an essential safety feature in cold weather and should be maintained in good condition.Full Answer >
Several different issues cause a central heating system to stop working. For instance, when the power is out, most systems no longer provide heat. Even though a forced air system uses natural gas as fuel, it may require electricity to operate the blower. If too many lights and electronics are on in the house, power overload can trip the electrical circuit breakers and affect the central heating system.Full Answer >