·
Most people will be familiar with the Van de Graff
generators and hair standing on end. Here is a more accurate explanation of
why. The force one point **Q _{1}** exerts on another point charge

·
F = __kQ _{1}q_{2 }__

r^{2}

·
K = 1/(4pe_{0})
where e_{0} is the permittivity of free space so

ü
F = __ 1 __ __Q _{1}q_{2 }__

4pe_{0 } r^{2}

·
Around electrical charges we can imagine an **electric
field**, a region in which an electric charge experiences a force.

ü F = QE

·
The direction of the field naturally depends on the charge,
the arrows are drawn to represent the direction of the force on a small
positive charge *+q*, so the field lines for a point positive charge go
radially outwards, those for a negative charge radially inwards. Hence a
repulsive force between two like-charged particles is taken to be positive.

·
As E=F/**q**, E=( kq_{1}q_{2}/r^{2})/**q**;

ü
E = __ 1 __ __Q __

4pe_{0 }r^{2}

·
Energy = F x d so, similar to gravitation, potential
energy E_{p} is given by

ü
E_{p} =__ 1 __ __Q _{1}q_{2 }__

4pe_{0 } r

·
Electrical potential is the potential energy per unit
charge (V=energy/q), so V=(kq_{1}q_{2}/r)/**q;**

ü
V = __ 1 __ __Q__

4pe_{0 }r

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2000

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