Science

Some Natural Phenomena

Types of Charges and their Interaction

We will select some objects from for the next activity.Let’s summarise the observations: A charged balloon repelled a charged balloon. A charged refill repelled a charged refill. But a charged balloon attracted a charged refill. 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 kind attract each other? It is a convention to call the charge acquired by a glass rod when it is rubbed with silk as positive. The other kind of charge is said to be negative. It is observed that when a charged glass rod is brought near a charged plastic straw rubbed with olythene there is attraction between the two. What do you think would be the kind of charge on the plastic straw? Your guess, that the plastic straw would carry a negative charge is correct. The electrical charges generated by rubbing are static. They do not move by themselves. When charges move, they constitute an electric current. You have been reading about electric current ince Class VI. The current in a circuit which makes a bulb glow, or the current that makes a wire hot. is nothing but a motion of charges.