Question

Assertion (A) : Alloys are commonly used in electrical heating devices
like electric iron and heater.
Reason (R) : Resistivity of an alloy is generally higher than that of its
constituent metals but the alloys have low melting points then their
constituent metals.​

Answer 1

The given Assertion (A) and Reason (R) both are True. Also, R is correct explanation of A.

• An Alloy is a combination of a metal with at least one other metal or nonmetal.
• An alloy is the combination  of a solid solution, a compound, or a mixture with another metal or nonmetal.
• Resistivity  depends on how free the crystal lattice is, i.e. more broader a road more freely a car can pass through.
• An Alloy has mixture of two metal ions,which are randomly arranged. This leads to more traffic in the path of electron flow. Hence,it causes more resistivity.
• But melting point of an alloy is much lower than that of its constituent pure metals. This is because the other metal behaves as an impurity in the metal,leading to lower melting point.
• An heating device requires constant flow on and flow off current through it. More the melting point of used metal is lower, more easier the connection can cut off, more easier the flow off of the current.
• Whereas, if the metal has greater melting point, then it takes lot of current to melt it and turn off the flow, which ultimately makes that electronic device more inefficient.
• So, an electronic device requires a metal with lower melting point. An alloy is perfect for the case.  

Answer 2

Both assertion and reason are true. The reason is correct explanation for assertion.

Explanation:

• The alloy is a mixture of two or more metals. The properties of all the mixed metals are seen in the property of alloy.
• The resistivity of the mixed metals increases the resistance of the alloy and melting point of the alloy decreases. It means low heat can melt the alloy.
• The alloys are used as solders in electronic devices which reduces the thermal stress on the electronic devices.
• The alloys are also used as connection with power socket because the high voltage will damage the electronic devices. Since, alloy have low melting point, it melts the connection of the device and protects device from further damage.