Coil present in electrical water heater made up of which alloy:
(A)- Nichrome
(B)- Steel
(C)- Brass
(D)- Aluminium bronze

Hint: The alloy is chosen depending on its resistance capability and mechanical strength. As the high resistance produces the heat energy in the appliance. And its mechanical strength makes it highly stable and less brittle in nature.

Complete step by step answer:
-The rod of the heater is made of the conducting material, which allows electricity to flow through it. At the bottom of the heater we have the coil which is made up of alloy, resulting in the conversion of the electricity provided into the heat energy in the appliance. This happens due to the resistance provided by the material of the coil, resulting in more heat production during the process.
-All the given compounds are alloy. These are formed by the mixing of a metal with one or more elements in the periodic table, which enhances the properties of the alloy compared to its constituent elements.
-The preferred alloy for the coil of the water heater is the Nichrome because of its high resistivity. As in its lattice arrangement consisting of the Nickel (80 %) and the Chromium (20%) metals, it leads to the formation of voids. On passing electricity, the electrons are scattered or their flow is disrupted by it leading to high resistance in the alloy.

Therefore, Coils present in electrical water heaters are made up of option (A)- Nichrome alloy.

Note: The nichrome also forms a chromium oxide layer on the coil, which prevents the further oxidation of the coil and its breaking on applying heat. So, the coil is protected. Thus, it is used in various appliances like ironing machines, iron soldering, hair dryers and e-cigarettes etc.