تاثير بلتير Peltier effect

## Peltier effect

Let’s first know about the main definition of what actually Peltier effect is .This is one of the three thermoelectric effects .Other two thermoelectric effects include Thomson and Seebeck Effect about which we will discuss later .The Peltier effect is a temperature difference created by applying a voltage between 2 electrodes connected to semiconductor material.

This effect is reversible in nature .

This effects has a significant importance when it is necessary to transfer heat from one medium to another medium on a small scale.

### Peltier Effect facts and history

• Peltier effect is named French physicist Jean Charles Athanase Peltier who discovered this effect in the year 1934 .Jean discovered a thermo-electric effect that was converse in nature to that of Seebeck effect .
• According to him when       we pass an electric current through 2 dissimilar conductor connected to form a thermo-couple ,there is evolution of heat at one junction and absorption at the other end.This heat evolution and heat absorption depends on direction of current flow .

## Peltier Coefficient

• Peltier coefficient has its own significant .It is defined as the amount of heat energy evolved or absorbed due to the peltier effect at two junctions of dissimilar metals when one Coulomb of charge is passed through that junction .
• Denotion of Peltier coefficient is π
• Peltier Coefficient has different value for different thermo-couple and its value changes with change in temperature of junction .

### Application of Peltier Effect / Uses of Peltier Devices

• Peltier-effect devices are used for the purpose of thermoelectric cooling   in large number of electronic equipment like computers .There fore these are best suitable when other conventional cooling methods look impractical.
• Some of the most used and common peltier effect devices are Peltier Cooler -A Peltier cooler (may be Peltier heater,Peltier Heat Pump, solid state refrigerator) is actually a solid-state active heat pump whose main function is to transfer heat from one side of the device to the other side against the temperature gradient by taking in electric current. When there is passage of Direct Current through this type of thermoelectric device,  heat passes from one side to the other side . Due to this one can use this device both as a heater and a cooler but mostly used for cooling purposes.

• Peltier devices like Peltier cooler can be used as temperature controller .

Refrigerator Based on Peltier Effect

• These devices are also used for the water extraction of water from air in dehumidifiers. Devices such as Thermal cyclers make use of peltier elements for DNA synthesis .
• The Peltier effect plays a very important role in spacecraft as it is used to balance the effect of direct sunlight on one side of the craft by dissipating amount of heat to the other side of spacecraft that does not receive sunlight, and therefore cooler.
• Advantages of these peltier devices includes that these are extremely reliable as they have no moving parts and hardly need any maintenance. But sometimes inefficient and emit quite a bit of heat due to which there is requirement of some additional device like a fan for heat dissipation .This comes under major drawback of peltier devices .

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