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Two Point Charges Q1 = 400 μC and Q2 = 100 μC Are Kept Fixed, 60 Cm Apart in Vacuum. Find Intensity of the Electric Field at Midpoint of the Line Joining Q1 and Q2. - Physics (Theory)

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Question

Two-point charges Q1 = 400 μC and Q2 = 100 μC are kept fixed, 60 cm apart in a vacuum. Find the intensity of the electric field at the midpoint of the line joining Q1 and Q2.  

Sum

Solution

`"E"_1 = "Q"_1/(4 piin_0 "r"_1^2)`  ... `["Q"_1 = 400mu"C" = 400 xx 10^-6"C"]`

`"E"_2 = "Q"_2/(4 piin_0 "r"_2^2)`  ...`["Q"_2 = 100mu"C" = 100 xx 10^-6"C"]`

∴ The resultant electric field

E = E2 - E1

`= "Q"_2/(4 piin_0 "r"_2^2) -  "Q"_1/(4 piin_0 "r"_1^2)`

`= 1/(4 piin_0 "r"^2)   ... ["Q"_2 - "Q"_1][because "r"_1 = "r"_2 = "r"]` 

`=(9 xx 10^9)/(30/100)^2 [400 - 100]xx10^-6`

`= (9xx10^11xx10^-6[3]xx100)/9`

`= 3 xx 10^7 "NC"^-1`

From Q1 to Q2 

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2015-2016 (March) Set 1

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