Concepts

Class 8
Chapter 15 Class 8 - Some Natural Phenomena

In this chapter, we will study two natural phenomena

• Lightning
• Earthquake

To learn about Lightning, we should first know what an electric charge is

## What is Charge

It is the amount of electricity contained in an object

There are 2 types of charges

1. Positive Charge
2. Negative Charge

## How is charge obtained?

It is obtained by friction caused by rubbing of 2 objects.

## What are Different Rules of Charge?

There are two rules of charges

• Like Charges Repel Each other
• Unlike Charges Attract Each other

### Like Charges Repel Each other

It means that if we bring 2 objects which have the same charge (both positive or both negative) together, they repel each other.

Example

Suppose we rub 2 balloon against wall, they become negatively charged.

If we bring both of them together, they repel each other

Similarly, if we bring 2 objects which are positively charged together

they repel each other

### Unlike Charges Attract each other.

It means that if we bring 2 objects, one Positively Charged and one Negatively Charged together,

they attract each other

Example

Suppose we rub a glass rod with silk, it becomes positively charged.

Similarly, if we rub a balloon against the wall ,it becomes negatively charged

Now, if we bring this charged glass rod with charged plastic straw, both attract as one is positively charged and other negatively charged

## Movement of Electric Charges

### Static Charge

Charge which does not move by themselves is called static charge

Charge which is generated by rubbing is static charge

### Electric Current

When charge moves, it constitutes Electric Current

Example

Current which make bulb glow.

Current which make wire heat

## Questions

NCERT Question 8 - Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?

NCERT Question 2 - When a glass rod is rubbed with a piece of silk cloth the rod

(a) and the cloth both acquire positive charge.

(b) becomes positively charged while the cloth has a negative charge.

(c) and the cloth both acquire negative charge.

(d) becomes negatively charged while the cloth has a positive charge

NCERT Question 3 (b) - Write T against true and F against false in the following statements:

A charged glass rod attract a charged plastic straw (T/F)

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