Question

Which of the following charges is acquired by silk when the silk is rubbed with glass?
A) Positive
B) Negative
C) Neutral
D) Cannot be determined

Answer 1

Hint: This question is based on the concept of static electricity. The same phenomenon that causes lightning. Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it can move away through electric current or electrical discharge. To overcome the difference in these charges or to make it balanced, the charges move from one object to another, that is why lighting is formed.

Complete step by step solution:
In the question, we are told that the glass is rubbed against the silk. During the process of rubbing the glass against silk, there is an increase in temperature on the surfaces of glass and silk, increasing the thermal energy of loosely bonded electrons present in the glass. So, these electrons move from the glass to the silk and now the glass has a deficiency of electrons. Hence, the glass acquires a partial positive charge.

On the other hand, the silk gets the electrons from the glass and acquires a negative charge on it. The charge formed is called the electrostatic charge. So, when the silk is rubbed with glass, silk acquires a negative charge.

Hence option (B), Negative is the correct answer.

Note: Further after the transfer of charge from the glass to silk takes place due to rubbing, if we take the glass and place it near pieces of paper, they get stuck to the glass rod. This is because the positive charge on the glass rod attracts the negative (electrons) on the surface of the pieces of paper. After a while, this doesn’t happen because the charge gets balanced. This phenomenon is called electrostatic induction.