Chapter 16: Q11Q (page 443)

When a charged ruler attracts small pieces of paper, sometimes a piece jumps quickly away after touching the ruler. Explain.

Short Answer

Expert verified

Sometimes a piece of paper jumps quickly away after touching the charged ruler because it acquires a charge of the same polarity as present on the ruler.

Step by step solution

Understanding the charging by induction

When charged object induces a charge of opposite polarity on another uncharged object without actually touching it, this process of developing the charge is referred to as charging by induction.

The charges that develop on the surface of the uncharged body are known as induced charges.

Explanation of reason behind the jumping of the piece of paper away from the ruler

When a charged ruler is brought near the small pieces of paper, the charge of opposite polarity is induced on the nearer surface of neutral pieces of paper. The charge of the same polarity gets collected on the farther surface. Therefore, these small pieces of paper get attracted towards the charged ruler.

However, if a piece of paper gets touched by the ruler, the paper receives charged by conduction, i.e., the piece of paper acquires a charge of the same polarity as the ruler. Therefore, charges being like repel each other, and thus the piece of paper jumps quickly away from the ruler.