11/14/2022 0 Comments Bi metal draft control![]() Can a bimetallic strip made of brass and silver be used in the thermostat? Yes, they are used in fans to convert temperature into mechanical displacement.īimetallic strips bend due to the metal thermal expansion property.ĥ). Case 2: When the temperature decreases it makes the strip expands towards the metal with a higher value of temperature coefficient, as shown below.Case 1: With the increase in temperature makes the strip expands towards the metal with the lower value of temperature coefficient, which can be observed in the below figure and.When a bimetallic strip is heated, the metals either expand or deform based on their thermal coefficient properties.What happens when a bimetallic strip is heated? The following are the applications of the bimetallic stripĪ bimetallic strip is used in devices like a fire alarm, fans, etc.Ģ). At low temperature, the sensitivity and accuracy are not up to the mark.There will be a change in the quality of metal on regular usage which may lead to an error while measuring.The following are the disadvantages of the bimetallic strip The following are the advantages of the bimetallic strip Usually, these kinds of thermometers are used in industrial applications. At this stage, the pointer records the temperature reading. Whenever the strip is heated, it experiences thermal expansion property and contracts on cooling. #Bi metal draft control freeWhere the free end of the strip is connected to a pointer. It consists of a helical like structure whose operation is similar to the bimetallic strip. These kinds of thermometers are usually used in recording ambient temperature. At this stage, the pointer records the temperature on the scale. When this spring structure is heated, then the metals exhibit thermal expansion property and it deforms when there is a fall in temperature. It consists of a spiral-like structure and a pointer is attached to it, which is used for scaling the temperature. Types of Bimetallic Stripsīimetallic strips are available in two types, they are Spiral Strip Type This kind of principle is usually observed in low sensitivity thermometers. = t/2 / ]įrom the above equation, we can conclude that if one end of the metallic strip is fixed, the other end of the strip expands or contracts on varying temperatures. r = Expanded Length of Expanded Strip A/Expanded Length of Expanded Strip B In a practical world, the ratio of metals moduli of elasticity and their thickness must be maintained equal so that the metal regains back to its normal position when the applied temperature changes. The equation for the metallic strip bending towards the metal with low-temperature coefficient is given as Α’ A, α’ B = Thermal coefficient of expansion metal A and B M = t1 / t2 = ( Lower thickness – expansion of metal) / (higher thickness – expansion of metal) N = E A / E B= ratio of elasticity of two metal T = ( t1 + t2) = sum of the thickness of the bimetallic strip It can be explained in the following two cases,Ĭase(i): When the temperature increases, it allows the strip to expand towards the metal with a lower value of temperature coefficient, which can be observed in the figure below. When applying temperature to these materials, then they will start to change their physical state either by expanding or by deforming. Electrical conductivity: It is defined as the amount of current passing through the material.Ī bimetallic strip is formed by bonding two different thin strips of metals usually steel ( 12 * 10 -6 K -1) & brass ( 18.7 * 10 -6 K -1), or copper ( 16.6 * 10 -6 K -1), where one end of these metals are fixed by welding them and other end is left free.This property varies from metal to metal. Elastic limit on cooling: It is the standard limit at which the metal gets back to its normal state on cooling.Elasticity modules: It is defined as the ratio of stress to strain in an elastic deformation region.Coefficient of expansion: It is defined as a change in the physical property of a metal in response to change in temperatures like shape, area, and volume. ![]()
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