What happens when a plastic ruler is rubbed vigorously with a woollen cloth?

When a plastic ruler is rubbed vigorously with a woollen cloth, several interesting phenomena occur due to the interaction between the materials. Let's explore the details below:

1. Electrostatic Charge Generation:
Rubbing the plastic ruler against the woollen cloth creates friction between the two surfaces. This friction causes the transfer of electrons between the materials, resulting in a buildup of static electricity. The plastic ruler tends to gain electrons, becoming negatively charged, while the woollen cloth loses electrons and becomes positively charged.

2. Triboelectric Effect:
The electric charge generated during the rubbing process is a result of the triboelectric effect. This effect occurs because different materials have different tendencies to gain or lose electrons when they come into contact and are then separated. In this case, the plastic ruler and woollen cloth have different electron affinities, leading to the charge transfer.

3. Polarization of Molecules:
As the rubbing process progresses, the strong electric fields created by the separated charges cause the alignment of molecules in the ruler and cloth. The molecules in the ruler become polarized, with the positive ends aligning towards the negatively charged cloth, and vice versa. This polarization enhances the interaction between the two materials.

4. Attraction and Repulsion:
Due to the opposite charges on the ruler and cloth, they experience an attractive force. The ruler is attracted to the cloth, and vice versa, as opposite charges attract each other. However, if two charged objects with the same charge are brought close together, they repel each other. This repulsion is observed when bringing the negatively charged ruler close to another negatively charged object.

5. Effect of Surrounding Objects:
The charged ruler can influence nearby objects. For example, if brought close to small pieces of paper, they may be attracted to the ruler due to the opposite charges. Additionally, if the ruler is brought close to a neutral object, it can induce a temporary charge separation in the neutral object, causing it to be attracted or repelled.

Overall, when a plastic ruler is rubbed with a woollen cloth, electrostatic charge is generated, leading to polarization, attraction, and repulsion effects. These phenomena are a result of the triboelectric effect and the interaction between the charges on the ruler and cloth.