Thursday , April 9 2020

NCERT 8th Class (CBSE) Science: Some Natural Phenomena

Question: Explain the working of electroscope.

Answer: When the brass disc of the electroscope is touched with a charged object, electric charge gets transferred to the gold leaf through the rod. This results in the gold leaves moving away from each other. This happens because both the leaves have similar charges.

Question: Explain the formation of lightning.

Answer: Formation of lightning takes place in following steps:

  1. During a thunderstorm, the air currents move upward and water droplets move downward. These movements take at very fast pace and it results in separation of charges in the clouds.
  2. The positive charges accumulate at the upper edges of the clouds and the negative charges accumulate at the lower edges of the clouds. Scientists are yet to understand the exact reason for this.
  3. At the same time, the ground becomes positively charged.
  4. Air is a bad conductor of electricity under normal circumstances. But when the amount of charge becomes too much in the clouds, the air is not in a position to hold on to this charge. As a result, the electric charge is transferred to the ground. This appears like a bright streak of light across the sky; which lasts for a few seconds.

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