Answer 1:
Electrical power lines can attract and repel
each other, but the amount of force involved is
incredibly small under most common conditions.
Current in two wires flowing in the same direction
attract each other, and currents in opposite
directions repel. The magnitude of this force
over a wire of length L (assuming the currents in
each wire are equal)
is F=mu*I^{2}*L/(2*pi*d)
where: mu is called the permeability
of free space (1.26*10^{6}
Newtons/Amp^{2}) I is the
current in the two wires L is the
length of the wire (meters) d is the
distance between the wires (meters) F
is the resulting force in Newtons, which can be
converted to pounds of force by multiplying by
0.225. To take an example typical of a high
power kitchen appliance like a water kettle, the
current in the two wires going to the outlet in
the wall is about 10A, and the distance between
them is about 5mm. Over a 1 meter wire length the
force is only 0.004 Newtons, which is a bit under
one thousandth of a pound, so it's very
small! So you can see that for pretty much
any case in day to day life electrical wires will
attract and repel each other, but it will be
unnoticeable because it is so small. One case
where these forces matter is in highpowered
electromagnets, like the superconducting
electromagnets in MRI machines. There the current
is high enough that the force is noticeable, and
the coil of wire has to be reinforced so that it
can hold its shape.
