Question

Sometimes, a cracking sound is heard while taking off sweaters during winters. Explain.

Answer 1

Hint: When surfaces of two materials are rubbed against each other, the force of friction comes into action. This force of friction as a result charges the atoms of the two materials in contact. In other words a transfer of electrons takes place between the two objects.

Complete step by step answer:
Objects are in general neutral in nature. In other words, they contain the same number of electrons and protons i.e., negative and positive charge. But when certain objects are rubbed against each other, one of them loses its electrons to the other, thus becoming positively charged. And the latter becoming negatively charged.

This phenomenon happens because in certain materials their electrons are very loosely bound to their outermost shell. Thus these electrons can easily be transferred to another body just by a little excitation that is by providing any form of sufficient energy to them.

When two bodies are rubbed against each force of friction comes into play. This force provides sufficient energy to one of the bodies to lose its electrons which are gained by the other. This results in static electricity.

Static electricity can be defined as an imbalance of charges between two bodies or on the surface of any material. This charge remains as it is until it is able to move away via an electric current. This is known as static discharge.

So, the discharge of electrons from the charged body causes sparks or shocks of static electricity. This is more likely to happen if the surroundings are dry.

Thus a cracking sound is heard while taking off sweaters during winters.

Note: A lot of other phenomena also take place due to static electricity like standing up by hair when removing a hat. And due to static discharge we get a shock from touching a metal door. Additionally, natural lightning is also due to static discharge.