Consider the following statements regarding the 'Convention' of charges: 1. The charge on a glass rod rubbed with silk is positive. 2. The charge on a plastic straw rubbed with polythene is positive. 3. Positive and negative charges repel each other. Which of the statements given above are correct?

Correct Option The correct option is (a). Explanation The concept of electric charge is based on the triboelectric effect (charging by friction) and the fundamental laws of electrostatics. Historically, Benjamin Franklin established the convention for naming charges as "positive" and "negative" based on specific material interactions. Statement-wise Analysis - Statement 1 is Correct: According to the standard convention of electrostatics, when a glass rod is rubbed with silk, the glass rod loses electrons and acquires a positive charge. The silk cloth, gaining electrons, acquires a negative charge. - Statement 2 is Incorrect: When a plastic straw (or rod) is rubbed with polythene (or fur), the plastic typically gains electrons due to its position in the triboelectric series. Consequently, the plastic acquires a negative charge, not a positive one. - Statement 3 is Incorrect: A fundamental property of electric charges is that like charges repel (positive-positive or negative-negative) and unlike charges attract (positive-negative). Therefore, positive and negative charges attract each other, they do not repel. Key Takeaway: By convention, a glass rod rubbed with silk is positively charged, while a plastic rod rubbed with fur is negatively charged. Fundamentally, like charges repel and unlike charges attract.

NCERT Class 8 Science — Chapter 3: Some natural phenomena

mcqeasy

Consider the following statements regarding the 'Convention' of charges:

The charge on a glass rod rubbed with silk is positive.
The charge on a plastic straw rubbed with polythene is positive.
Positive and negative charges repel each other.

Which of the statements given above are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A1 only
B2 only
C1 and 3 only
D1, 2 and 3

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Solution

Correct Option

The correct option is (a).

Explanation

The concept of electric charge is based on the triboelectric effect (charging by friction) and the fundamental laws of electrostatics. Historically, Benjamin Franklin established the convention for naming charges as "positive" and "negative" based on specific material interactions.

Statement-wise Analysis

Statement 1 is Correct: According to the standard convention of electrostatics, when a glass rod is rubbed with silk, the glass rod loses electrons and acquires a positive charge. The silk cloth, gaining electrons, acquires a negative charge.
Statement 2 is Incorrect: When a plastic straw (or rod) is rubbed with polythene (or fur), the plastic typically gains electrons due to its position in the triboelectric series. Consequently, the plastic acquires a negative charge, not a positive one.
Statement 3 is Incorrect: A fundamental property of electric charges is that like charges repel (positive-positive or negative-negative) and unlike charges attract (positive-negative). Therefore, positive and negative charges attract each other, they do not repel.

Key Takeaway: By convention, a glass rod rubbed with silk is positively charged, while a plastic rod rubbed with fur is negatively charged. Fundamentally, like charges repel and unlike charges attract.

Your note

More from Chapter 3: Some natural phenomena

With reference to the history of understanding electrical charges, consider the following statements: 1. The ancient Greeks knew that amber attracts light objects like hair when rubbed with fur. 2. Benjamin Franklin proved that lightning and sparks from clothes are two completely different phenomena. 3. The realization of the similarity between lightning and sparks from clothes took approximately two thousand years to occur. Which of the statements given above is/are correct?

medium

Consider the following statements regarding the charging of objects by rubbing: 1. A plastic refill does not acquire any electric charge when rubbed with polythene. 2. When a plastic comb is rubbed with dry hair, both the comb and the hair get charged. 3. The electrical charges generated by rubbing are static in nature. Which of the statements given above is/are correct?

medium

With reference to the interaction between charged objects, consider the following statements: 1. A charged balloon repels another charged balloon. 2. A charged refill repels a charged balloon. 3. A charged refill attracts another charged refill. Which of the statements given above are correct?

easy

By convention, what is the nature of the electric charge acquired by a glass rod when it is rubbed with silk?

easy

Consider the following statements regarding the nature of electric charges: 1. Charges of the same kind repel each other. 2. Charges of different kinds repel each other. 3. A charged glass rod attracts a charged plastic straw rubbed with polythene. Which of the statements given above is/are correct?

medium

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Correct Option

The correct option is (a).

Explanation

Statement-wise Analysis

Statement 1 is Correct: According to the standard convention of electrostatics, when a glass rod is rubbed with silk, the glass rod loses electrons and acquires a positive charge. The silk cloth, gaining electrons, acquires a negative charge.
Statement 2 is Incorrect: When a plastic straw (or rod) is rubbed with polythene (or fur), the plastic typically gains electrons due to its position in the triboelectric series. Consequently, the plastic acquires a negative charge, not a positive one.
Statement 3 is Incorrect: A fundamental property of electric charges is that like charges repel (positive-positive or negative-negative) and unlike charges attract (positive-negative). Therefore, positive and negative charges attract each other, they do not repel.