The different expansions force the flat strip to bend one way if heated, and in the opposite direction if cooled below its initial temperature. The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled.
The sideways displacement of the strip is much larger than the small lengthways expansion in either of the two metals. This effect is used in a range of mechanical and electrical devices. In some applications the bimetal strip is used in the flat form. In others, it is wrapped into a coil for compactness. The greater length of the coiled version gives improved sensitivity. The earliest surviving bimetallic strip was made by the eighteenth-century clockmaker John Harrison who is generally credited with its invention.
He made it for his third marine chronometer H3 of to compensate for temperature-induced changes in the balance spring. His earliest examples had two individual metal strips joined by rivets but he also invented the later technique of directly fusing molten brass onto a steel substrate. A strip of this type was fitted to his last timekeeper, H5. Harrison's invention is recognized in the memorial to him in Westminster Abbey , England. Mechanical clock mechanisms are sensitive to temperature changes as each part has tiny tolerance and it leads to errors in time keeping.
A bimetallic strip is used to compensate this phenomenon in the mechanism of some timepieces. The most common method is to use a bimetallic construction for the circular rim of the balance wheel. What it does is move a weight in a radial way looking at the circular plane down by the balance wheel, varying then, the momentum of inertia of the balance wheel. As the spring controlling the balance becomes weaker with the increasing temperature, the balance becomes smaller in diameter to decrease the momentum of inertia and keep the period of oscillation and hence timekeeping constant.
Nowadays this system is not used anymore since the appearance of low temperature coefficient alloys like nivarox , parachrom and many others depending on each brand. In the regulation of heating and cooling, thermostats that operate over a wide range of temperatures are used. In these, one end of the bimetallic strip is mechanically fixed and attached to an electrical power source, while the other moving end carries an electrical contact. What happens when a bimetallic strip is heated?
Yes, they are used in fans to convert temperature into mechanical displacement. Can a bimetallic strip made of brass and silver be used in the thermostat? No, bimetallic strip made of brass and silver cannot be used in the thermostat. Since they have a negligible difference in their thermal expansion property.
Thus, this is all about an overview of a bimetallic strip which works on two main fundamental thermal expansion and temperature coefficient.
It is usually a thermometer device that measures temperature. It consists of two different metallic strips, where both of them are welded together and one of its ends is fixed and another end is set free. Theses metals expand or deform at varying temperatures. They are available in two forms helical and spiral form. Where helical bimetallic strip thermometer is used in industrial areas, and the spiral bimetallic thermometer is used in less sensitive areas.
Here is a question for you, what is the function of the bimetallic strip? The metal with the higher coefficient of thermal expansion is on the outer side of the curve when the strip is heated and on the inner side when cooled. The sideways displacement of the strip is much larger than the small lengthways expansion in either of the two metals.
This effect is used in a range of mechanical and electrical devices. In some applications the bimetal strip is used in the flat form. In others, it is wrapped into a coil for compactness. The greater length of the coiled version gives improved sensitivity.
The earliest surviving bimetallic strip was made by the eighteenth-century clockmaker John Harrison who is generally credited with its invention. He made it for his third marine chronometer H3 of to compensate for temperature-induced changes in the balance spring.
It should not be confused with his bimetallic mechanism for correcting for thermal expansion in the gridiron pendulum. His earliest examples had two individual metal strips joined by rivets but he also invented the later technique of directly fusing molten brass onto a steel substrate.
A strip of this type was fitted to his last timekeeper, H5. Harrison's invention is recognized in the memorial to him in Westminster Abbey, England. Click Here to Know about a Legend Dr. Abdul Kalam. Toggle navigation Menu. Social Discuss Sign Up Login.
Bimetallic Strip Famous Inventors. Home inventions Bimetallic Strip. Bimetallic Strip - Invented by John Harrison. Invented Year.
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