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## Homework Statement

An electric field is created by an uniform linear charge with a linear charge density is 40 nC/m. Find the potential difference between the two points, one of which is situated 5 cm from the line charge and the second at 10cm.

Two charges, q and -3q, are situated at a distance of 70 cm from each other. At which point will a charge q1 be in equilibrium position in the electric field created by the two above mentioned charges?

## Homework Equations

No integrals or derivatives, the teacher said.

E = lambda/2*pi*e0*r

E = V/m

F = kQ1Q2/r**2

## The Attempt at a Solution

First one:

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So, I know that it is a line charge field thus E = lambda/2*pi*e0*r, and that E = V/m so in my logic the voltage of both point 1(5 cm) and point 2(10cm) would be the same, because dividing their electric field by their respective distances would lead to their potential difference being 0. But I know that the potential increases as you get away from the linear charge.

**Second One**

Should I compare them both with Coulomb's law? I also have some issue understanding what the teacher is actually asking, is he talking about a third charge being put on the field and the point at which all of them would be in equilibrium? My teacher's spoken English is very good, but I find it somewhat troublesome to understand his writing sometimes.