Question

Assertion- Alloys are commonly used in electrical heating devices like electric iron and heater.

Reason- The resistivity of an alloy is generally higher than that of its constituent metals but the alloys have low melting points than their constituent metals.

Choose the correct option:

• A. Both assertion and reason are true and reason is the correct explanation of assertion.
• B. Both assertion and reason are true but reason is not the correct explanation of assertion.
• C. Assertion is true but reason is false
• D. Assertion is false but reason is true

Answer 1

The correct option is A

Both assertion and reason are true and reason is the correct explanation of assertion.

Alloy: The homogeneous mixture of two or more metals or non-metals to improve their various properties of them, is called an alloy.

For example, aluminium $\left(\mathrm{Al}\right)$ is light but not strong, but an alloy of aluminium with copper $\left(\mathrm{Cu}\right)$, magnesium $\left(\mathrm{Mg}\right)$ and manganese $\left(\mathrm{Mn}\right)$ called duralumin is light as well as strong. It is used for making aircraft bodies and parts, space satellites and kitchenware.

More examples are: Brass is an alloy of copper $\left(\mathrm{Cu}\right)$ and zinc $\left(\mathrm{Zn}\right)$, Bronze is an alloy of copper $\left(\mathrm{Cu}\right)$ and tin $\left(\mathrm{Sn}\right)$, etc.

The properties of an alloy are different from the properties of the constituent metals:

1. Alloys are stronger than the metals from which they are made.
2. Alloys are harder than their constituent metals.
3. Alloys are more resistant to corrosion.
4. Alloys have lower melting points than constituent metals.
5. Alloys have lower electrical conductivity than pure metals.

Alloys are used in electrical appliances -the reason

• Alloys generally have a high melting point as compared to individual elements.
• The electrical heating devices must have a high melting point so that they do not melt even at high temperatures when an electrical current passes through a device.
• Thus alloys are used in the electrical heating devices.

The given assertion is “Alloys are commonly used in electrical heating devices like electric iron and heater” is true due to the low melting point, it takes less current to melt and leads to the fast movement of electrons which makes the device more efficient.

Hence, the correct option is (A) Both assertion and reason are true and the reason is the correct explanation of assertion.