Two point charges `q_(A)=3muC` and `q_(B)=-3muC` are located 0.2 m apart in vacuum.
a. What is the electric field at the mid point O of the line AB joining the two charges?
b. If a negative test charge of magnitude `1.5xx10^(-9)C` is placed at this point, what is the force experienced by the test charge?

Explanation

Given `q_(A) = 3xx10 ^(-6) C, q_(B )=-3xx10^(-6)C,`
`r=0.20 m`
Electric dfield at the midpoint .0.

wkt `=E = (9xx10 ^(9))/(r^(2))Vm^(-1)`
Hence `E_(A) = E_(B ) =(9xx10 ^(9)xx3xx10 ^(-6) )/((0.10)^(2))`
i.e., `E_(A) E_(B ) =(27xx10 ^(3))/(10 ^(-2))`
`=27 xx10^(5) VM ^(-1)`
the direction along AB or OB .
` therefore ` Net electric field at `=E_(A) +E_(B)`
`=5.4 xx10 ^(6) Vm^(-1) along OB `