12.3. Types of Charges and Their Interaction

In this activity we have brought close together the charged objects that were made of the same material. What happens if two charged objects made of different materials are brought close to each other? Let’s find out.

In this section, we focus on how different types of charges interact. When you rub two similar objects (like balloons) with a woollen cloth, they both gain the same type of charge. When you bring them close to each other, they repel each other, meaning they push away from each other. This occurs because like charges repel each other.

Think of two people with similar personalities trying to occupy the same space in a crowded room. They will likely push against each other as they try to maintain their personal space, just as two similarly charged balloons repel each other.

Activity 12.3 (a): Inflate two balloons. Hang them in such a way that they do not touch each other. Rub both the balloons with a woollen cloth and release them. What do you observe?

In this activity, you rub two balloons with a woollen cloth, which gives them a charge. When released, you will notice that the balloons will move away from each other, demonstrating the principle that like charges repel. This observation reinforces the idea that charges can have a significant effect on the movement of objects.

Imagine two magnets with the same pole facing each other (like north to north). They will repel each other and move apart. This is similar to what happens with the two charged balloons.

Repeat this activity with the used pen refills. Rub one refill with polythene. Place it carefully in a glass tumbler. Bring an inflated charged balloon near the refill and observe.

When you rub a refill with polythene, it becomes charged. If you bring this charged refill close to a charged balloon (which has a different charge because of the material), you will find that they attract each other. This indicates that charges of opposite types (negative and positive) attract each other, while charges of the same type repel.

Consider magnets again: if you have one north pole magnet and one south pole magnet, they will pull towards each other while the two north poles will push away. Similarly, unlike charges attract while like charges repel.

Does it indicate that the charge on the balloon is of a different kind from the charge on the refill? Can we say then, that there are two kinds of charges? Can we also say that the charges of the same kind repel each other, while charges of different kinds attract each other?

This section discusses the conclusion derived from observing the interactions between different charges. It establishes that there are two distinct types of electric charges: positive and negative. Positive charges repel other positive charges, and negative charges repel other negative charges, but positive and negative charges attract each other.

Think of how our social interactions can work similarly. If two people with similar dislikes meet, they may avoid each other (like charges repel). However, if someone with a different opinion arrives, they might connect better (like positive and negative charges attract).

It is observed that when a charged glass rod is brought near a charged plastic straw rubbed with polythene, there is attraction between the two. The electrical charges generated by rubbing are static. They do not move by themselves. When charges move, they constitute an electric current.

This part clarifies that static electricity results from charges that remain stationary after being generated by friction between materials. The movement of these charges is what creates electric current, the flow of electric charge that powers devices and lights.

Imagine a water tank filled to the brim (static charges) versus a hose with water flowing through it (electric current). The water in the tank does not move until tapped, much like static charges, whereas the hose is synonymous with the movement of current.

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