Answer the Questions Based on Paragraph - Physics

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Meeta's father was driving her to school. At the traffic signal, she noticed that each traffic light was made of many tiny lights instead of a single bulb. When Meeta asked this question to her father, he explained the reason for this.

Answer the following questions based on above information:

(i) What were the values displayed by Meeta and her father?

(ii) What answer did Meeta's father give?

(iii) What are the tiny lights in traffic signals called and how do these operate?

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​​​​(i) Following values were displayed by Meeta and her father:

Meeta: Curiosity

Her father: Patience and knowledge

(ii) Meeta’s father probably explained her the benefits of using LEDs instead of a large incandescent bulb in the traffic lights. The benefits of LEDs over large single bulb are listed below:

(a) LEDs consume very less power, so they are preferred over bulbs. LEDs used in the traffic light consume less power than a large incandescent single bulb.
(b) The cost of a tiny LED is much less than that of an incandescent bulb and therefore, the maintenance cost of traffic signals is reduced.
(c) Even if a few bulbs are not working, the working of the traffic light will remain unaffected. On the other hand, if the one large incandescent bulb fuses, then the traffic light will stop working.

(iii) These tiny lights are called LEDs (Light Emitting Diodes) and they work on the principle of de-excitation of electrons in a forward-biased semiconductor upon the passing of electricity through them.
Concept: Special Purpose P-n Junction Diodes
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2015-2016 (March) Delhi Set 1

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