Question

Возьмите лист бумаги ,прижмите его к стене и отпустите . видно что он моментально падает .но если лист прижатый к стене потереть шерстяной тканью то он некоторое время продержится на стене как приклеенный .как можно объяснить это явлении ?

Answer 1

При натирании лист бумаги электризуется. При электризации лёгкие тела получают свойства притягиваться. 

Answer 2

Explanation of the Phenomenon

The phenomenon you described, where a piece of paper falls immediately when released from being pressed against a wall, but remains stuck to the wall for some time when rubbed with a woolen cloth, can be explained by static electricity.

When you press the paper against the wall and then release it, gravity pulls the paper downward, causing it to fall. However, when you rub the paper with a woolen cloth, it becomes charged with static electricity. This static charge creates an attraction between the paper and the wall, allowing the paper to stick to the wall for a period of time.

Static Electricity and Attraction

Static electricity is the buildup of electric charge on the surface of an object. When two objects come into contact and then separate, electrons can be transferred between them, resulting in a difference in electric charge. This difference in charge creates an electric field, which can cause objects to attract or repel each other.

In the case of the paper and the wall, rubbing the paper with a woolen cloth transfers electrons from the cloth to the paper, giving the paper a negative charge. The wall, on the other hand, becomes positively charged. The opposite charges attract each other, causing the paper to stick to the wall.

Duration of the Phenomenon

The duration for which the paper remains stuck to the wall after being rubbed with a woolen cloth depends on various factors, such as the amount of static charge transferred to the paper, the humidity in the air, and the smoothness of the wall's surface. Over time, the static charge on the paper dissipates, and the attraction between the paper and the wall weakens, causing the paper to eventually fall.

It's important to note that the phenomenon you described is temporary and can be easily disrupted by external factors, such as air currents or changes in humidity.

Conclusion

In summary, the phenomenon you observed, where a piece of paper falls immediately when released from being pressed against a wall but remains stuck to the wall for some time when rubbed with a woolen cloth, can be explained by static electricity. Rubbing the paper with a woolen cloth transfers a static charge to the paper, creating an attraction between the paper and the wall. This attraction allows the paper to stick to the wall for a period of time before the static charge dissipates and the paper falls.