The occurrence of lightning is as follows. The formation of clouds involves friction between water particles in the atmosphere. The friction charges the particles. Among the positive and negative charges, the negative charge accumulates at the bottom of the cloud and the positive charges in its top. As the accumulation of the charge increases, the cloud will create a positive charge on the ground nearby. As the amount of charge increases, the negative charge on the cloud tends to make a path towards the ground, and it results in a narrow streak of electrical discharge, which we call lightning.
An electroscope is a device that detects the type of charge on a body. Like charges repel and unlike charges attract each other. This is used in an electroscope. An electroscope consists of a glass jar fitted with a cork lid and a metallic wire passing through it. There are two metallic strips at the bottom of the wire. The upper end of the wire is connected to a metal disc. A body that is positively charged is touched to the metal disc, so that the charge is transferred to the metal strips through the wire, and they diverge from each other on gaining a like charge. Now, if a negatively charged object is brought into contact with the disc, the strips converge towards each other, indicating the unlike charge on the body. Similarly, if a positively charged body is brought in contact with the metal disc, the divergence of the metal strips increases, indicating the like charge on the body. If the metal disc of the electroscope is touched with the hand, it loses its charge to the ground by transfer of charge through the human body. This is called earthing.
View NCERT Solution
- Chapter-wise tests to help you assess your preparation status after studying a chapter.
- Detailed solutions for all the tests help students compare their solutions with model answers provided.
- Unlimited tests for extensive practice.
- Notes are organized chapter-wise for quick and easy reference.
- Available in easily downloadable PDF format for easy downloading and printing.
- High-quality illustrations and supporting diagrams aid in quick understanding.
- Point-wise summary of key concepts in a chapter to ensure that you cover all topics.
- Textbook revise are available in PDF format for easy download and printing.
- Concepts are explained in easy language accompanied with high-quality graphics.