Assertion (A) : The metals and alloys are good conductors of electricity. Reason (R) : Bronze is an alloy of copper and tin and it is not a good conductor of electricity.

Q: Assertion (A) : The metals and alloys are good conductors of electricity. Reason (R) : Bronze is an alloy of copper and tin and it is not a good conductor of electricity.

The correct option is **(d)**: (A) is false but (R) is true. **Explanation:** * **Assertion (A) is false:** While pure metals are excellent conductors of electricity, alloys generally have much lower electrical conductivity than their constituent pure metals. Therefore, saying alloys are "good conductors of electricity" in a general sense is incorrect. * **Reason (R) is true:** Bronze is an alloy of copper ($\text{Cu}$) and tin ($\text{Sn}$). It is a poor conductor of electricity compared to pure copper, which is why pure copper (and not bronze) is used for making electrical transmission wires.

Metals and Non-metals

Physical Properties of Metals and Non-metals

Options

(a)Both (A) and (R) are true and (R) is correct explanation of the assertion.

(b)Both (A) and (R) are true but (R) is not the correct explanation of the assertion.

(c)(A) is true but (R) is false.

(d)(A) is false but (R) is true.

Official Answer

The correct option is (d): (A) is false but (R) is true.

Explanation:

Assertion (A) is false: While pure metals are excellent conductors of electricity, alloys generally have much lower electrical conductivity than their constituent pure metals. Therefore, saying alloys are "good conductors of electricity" in a general sense is incorrect.
Reason (R) is true: Bronze is an alloy of copper ( $\text{Cu}$ ) and tin ( $\text{Sn}$ ). It is a poor conductor of electricity compared to pure copper, which is why pure copper (and not bronze) is used for making electrical transmission wires.

alloybronzecopper and tinpoor conductorelectrical conductivity

Marking Scheme

11 mark for selecting the correct option (d) with a valid scientific justification.

Hint

Think about whether alloys conduct electricity as efficiently as pure metals. Remember that copper is used for electrical wiring, but its alloy bronze is not.

Quick Oral Answer

Alloys have lower electrical conductivity than pure metals because the addition of foreign atoms disrupts the orderly arrangement of the metal lattice, scattering the conducting electrons and increasing resistance.

Analysis & Explanation

In Class 10 CBSE Science, the electrical conductivity of metals and their alloys is compared. Pure metals like copper and aluminium have high electrical conductivity due to the presence of free electrons. However, when a metal is alloyed with another metal or non-metal, the regular crystal lattice is disrupted, which significantly reduces the mobility of free electrons. Consequently, alloys like brass (copper and zinc) and bronze (copper and tin) are poor conductors of electricity. Thus, the assertion that both metals and alloys are good conductors is false, while the reason stating bronze is an alloy of copper and tin and is a poor conductor is scientifically correct.

Common Mistakes

1Students often assume that because alloys are made of metals, they must retain high electrical conductivity.
2Confusing bronze (copper + tin) with brass (copper + zinc).

Interesting Facts

Even though bronze is a poor electrical conductor, its high resistance to corrosion and friction makes it excellent for marine applications, musical instruments, and medals!

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2020?

This question carries 1 mark in the CBSE Class 10 Science 2020 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Metals and Non-metals" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Physical Properties of Metals and Non-metals" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2020 paper?

This is a MCQ question from Section A in the CBSE Class 10 Science 2020 paper.