Name the material which is used for making the heating element of an electric iron.

Name the form of polyester which is replacing materials like glass and used for making bottles and jars.

What are the outside raw materials used for by an organism?.

Which of the following statements is not true?(a) Materials are grouped for convenience.(b) Materials are grouped to study their properties.(c) Materials are grouped for fun.(d) Materials are grouped according to their uses.

Observe the bins and waste material heaps and suggest what materials can be used for preparing handicrafts materials.

Give two reasons why nichrome alloy is used for making the heating elements of electrical appliances.

This portion of the element will finally get failed. If the heating element directly comes in contact with the chemical fumes during industrial operations, this will corrode the region of the element where fumes touch the element. This shows that there is a comparatively higher operating temperature at the particular spot as compared to the rest of the element. In case of formation of hot spots, the point of failure of the heating element is the place where the element shines brightest during the operation. Now, for the further operation, the inner surface gets oxidized and thus, the effective cross-section at such spots becomes comparatively smaller resulting into formation of hot-spots and finally breakdown. During switching operation, the oxide layer gets flack off and exposing the inner surface to the atmosphere. The outermost surface of the heating element gets oxidized at high temperatures.

This portion of the element will produce more heat and get failed. During the process of alloying, a portion may have a higher content of the higher resistivity constituent. The mechanical failure of the heating element is mainly due to production of more heat. The following table gives the names of alloys, composition and their safe operating temperature for different alloys used as heating element − Name of Alloyįollowing are the factors responsible for the failure of heating elements − The Ni-Cr-Fe alloy is suitable for temperature up to 850 ☌.įor temperatures above 1200 ☌, the heating elements are made of silicon carbide, molybdenum, tungsten and graphite. The addition of iron to the alloy decreases the temperature at which oxidation takes place and hence the cost of product also reduces. The Ni-Cr alloy is suitable for temperature up to 1200 ☌.Īlloy of Nickel, Chromium and Iron, where Ni = 65%, Cr = 15% and Fe = 20%.

The alloys commonly used for low and medium temperature services are −Īlloy of Nickel and Chromium, where Ni = 80 % and Cr = 20%.

The various heating alloys are given as follows − Different alloys have been tried to obtain different temperature. No single element, metallic or non-metallic, is used for designing the heating elements. An electric heating element is a device which converts electrical energy input into heat energy output.

Heating element