Name the kind of electroscope that can be reconized as being charged, just by observation. Explain why.

The kind of electroscope that can be recognized as being charged just by observation is called a gold-leaf electroscope. This type of electroscope consists of a metal rod with a metal disk at the top, and two thin gold leaves attached to the bottom.

When the electroscope is charged, it means that excess charge has been transferred to either the metal rod or the metal disk at the top. This excess charge causes the two gold leaves to repel each other and move apart. By observing the movement of the gold leaves, one can determine if the electroscope is charged or not.

The reason behind this behavior lies in the principle of electrostatics. Like charges repel each other, while opposite charges attract. When the electroscope is charged, the excess charge on the rod or the disk repels the electrons in the gold leaves, causing them to move away from each other.

To observe the charge of a gold-leaf electroscope, you can follow these steps:
1. Ensure that the electroscope is in a neutral state by touching the metal rod with your hand. This neutralizes any previous charge.
2. Bring a charged object, such as a plastic rod that has been rubbed with a cloth, near the metal disk of the electroscope without touching it.
3. Observe the movement of the gold leaves. If they diverge or spread apart, it indicates that the electroscope has acquired a charge.

By understanding the underlying principles of electrostatics and using a gold-leaf electroscope, you can easily recognize if the electroscope is charged or not just by observing the movement of the gold leaves.