CBSE Class 12-science Answered
answer
![question image](http://images.topperlearning.com/topper/new-ate/top_mob168481769582709828answer6854745758884501582.jpg)
Asked by r01raunak | 23 May, 2023, 10:24: AM
The question is guessed from the scribbling shown in the image as follows
" It is required to find the location of null electric field between the charges 30 μC and 40 μC if the distance between two charges is 20 m"
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![](https://images.topperlearning.com/topper/tinymce/imagemanager/files/58f1315a223798ed178259da31070b2e646c5317231300.00509441f3.png)
Let us assume that at point P which is at a distance x m from 30 μC charge we have null electric field .
Let E1 and E2 be the electric field due to 30 μC and 40 μC charge respectively.
![begin mathsize 14px style E subscript 1 space equals space K space asterisk times space fraction numerator 30 space cross times space 10 to the power of negative 6 end exponent over denominator x squared end fraction end style](https://images.topperlearning.com/topper/tinymce/cache/23b895d4ea19b9f440afcf57da12e071.png)
where K = 1 / (4 πεo ) is Coulomb's constant .
![begin mathsize 14px style E subscript 2 space equals space K space asterisk times space fraction numerator 40 space cross times space 10 to the power of negative 6 end exponent over denominator left parenthesis 20 minus x right parenthesis squared end fraction end style](https://images.topperlearning.com/topper/tinymce/cache/07f691290e48caff31d04b8cdb4d6fd8.png)
If we get null electric field at P , then E1 = E2
![begin mathsize 14px style 30 over x squared space equals space 40 over left parenthesis 20 minus x right parenthesis squared end style](https://images.topperlearning.com/topper/tinymce/cache/5ee7861a002b65522950d5e58f69e673.png)
![begin mathsize 14px style 40 space x squared space equals space 3 space left parenthesis 20 space minus space x space right parenthesis squared space end style](https://images.topperlearning.com/topper/tinymce/cache/d953d2ce964f61a34a549f676cc1f9a3.png)
![begin mathsize 14px style space square root of 4 over 3 end root space x space equals space left parenthesis space 20 space minus x space right parenthesis end style](https://images.topperlearning.com/topper/tinymce/cache/a5c55ba588ba8779b1971bf8d7a3802a.png)
1.155 x = (20 -x )
2.155 x = 20
x = 20 / 2.155 = 9.28 m
Hence at a distance 9.28 m from 30 μC charge , we get zero electric field
Answered by Thiyagarajan K | 23 May, 2023, 11:32: AM
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