Explanation:
When a silk cloth is rubbed against a glass rod, the silk rod will acquire a negative charge. This can be explained by the process of static electricity and the transfer of electrons.
Here is a detailed explanation of why the silk rod gets a negative charge:
1. Electron transfer: When the silk cloth is rubbed against the glass rod, there is a transfer of electrons between them. The glass rod loses some of its electrons, while the silk cloth gains those electrons.
2. Electron affinity: The silk cloth has a higher affinity for electrons compared to the glass rod. This means that it has a stronger attraction for electrons and is more likely to gain them during the rubbing process.
3. Triboelectric series: The triboelectric series is a list that ranks materials based on their tendency to gain or lose electrons when in contact with other materials. According to this series, silk has a higher tendency to gain electrons, while glass has a lower tendency to lose electrons.
4. Charge separation: As the silk cloth gains electrons from the glass rod, a charge separation occurs. The glass rod becomes positively charged because it loses electrons, while the silk cloth becomes negatively charged because it gains electrons.
5. Charge transfer: The rubbing action allows for the transfer of charges between the two materials. The friction between the silk cloth and the glass rod creates an imbalance of charges, resulting in the silk rod acquiring a negative charge.
In conclusion, when a silk cloth is rubbed against a glass rod, the silk rod acquires a negative charge due to the transfer of electrons. This is because the silk cloth has a higher electron affinity and a greater tendency to gain electrons compared to the glass rod.

Explanation:

Frictional Charging:
When a silk cloth is rubbed against a glass rod, a process called frictional charging occurs. During this process, electrons are transferred between the two materials, leading to one material becoming positively charged and the other becoming negatively charged.

Positive Charge:
In the case of rubbing a silk cloth against a glass rod, the silk cloth will acquire a negative charge. This is because the silk cloth has a greater affinity for electrons compared to the glass rod. As a result, electrons are transferred from the glass rod to the silk cloth, leaving the silk cloth with an excess of electrons and thus a negative charge.

Effect of Rubbing:
The act of rubbing the silk cloth against the glass rod facilitates the transfer of electrons between the two materials. This rubbing action generates friction, which in turn causes electrons to be pulled from the glass rod onto the silk cloth, leading to the observed charging effect.

In conclusion, when a silk cloth is rubbed against a glass rod, the silk cloth will acquire a negative charge due to the transfer of electrons from the glass rod. This phenomenon is a result of frictional charging and the differing electron affinities of the two materials.