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1. Electric Charges and Fields
normal
Two identical point charges are placed at a separation of $ l.$ $P$ is a point on the line joining the charges, at a distance $x$ from any one charge. The field at $P$ is $E$. $E$ is plotted against $x$ for values of $x$ from close to zero to slightly less than $l$. Which of the following best represents the resulting curve?
A
B
C
D
Solution
Let $q$ be the charge of two identical point charges.
The electric field at $\mathrm{P}$ is $E=k q\left[\frac{1}{(L-x)^{2}}-\frac{1}{x^{2}}\right]$
at $x=0, E=k q \frac{1}{L^{2}}$
at $x=L, E=-k q \frac{1}{L^{2}}$
As $E$ varies inversely with square of the distance so $(D)$ represents the best resulting curve.
Standard 12
Physics
