Equipotentials around a charge Q

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To find the value of a point charge Q given an equipotential of 40V at a distance of 0.4cm, the correct equation is V = Q/(4πε₀r). The user is unsure about the value of ε, which is the permittivity of free space, and can be approximated as 8.85 x 10^-12 C²/(N·m²). It's important to convert the distance from centimeters to meters for accurate calculations. Using the provided value of 1/(4πε₀) = 9 x 10^9 N·m²/C² will aid in solving the problem.
ghostbuster25
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Hi there,

im having trouble finding the right equation for a problem I've got.

I have a point charge with an equipotential of 40v at 0.4cm. I am suppossed to work out the value of the charge.

Ive tried

q/4\pi\epsilonr

but it doesn't work and i think its because I am not putting in a value for \epsilon
as i don't know what it is.

cols anyone tell me if a, I am using the right equation and b, hot to find or put in the value of \epsilon

many thanks
 
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You can use the value 1/4πε0 (the whole thing) = 9x109 N m2/C2. Don't forget to convert centimeters to meters.
 

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