Can a tech savvy FReeper explain how power "leaks" from transmission lines? I should think they'd be well insulated.
Get within 5 feet of a High Tension Wire and it will Arc Out to you.
High voltage lines are not insulated at all.
my attempt to answer your actual question......
1. magnetism makes electricity
2. electricity makes magnetism......both statements are true
power lines are surrounded by magnetic fields, which induce "electricity" into conductive objects.
an ignition coil or common power-pack/transformer is one example of induction at work.....i.e. no actual physical connection
Transmission lines are not insulated at all. But that is not the problem. The problem is caused my the magnetic fields surrounding the conductors which is huge on the high voltage lines. If you remember from science class, to generate electricity you need a moving conductor and a magnetic field or a moving magnetic field and a conductor.
Because the power lines are AC the magnetic field is building, collapsing and changing direction with every cycle of the current.
Huge, strong, moving magnetic field + stationary metal objects and wiring in the house = generated electricity
Not to pile on, but power lines have associated magnetic and electrical fields. Insulation does not effectively confine the electric field, it only prevents current flow from the conductor. Insulating high voltage lines would not be practical.
Both the Electric and Magnetic fields associated with balanced power lines fall off as the inverse square of distance. Most of the energy stored in a power line is in the magnetic field (power lines look like inductors) but close to the lines the electrical field can be objectionable as well. If you stand close enough to a power line and hold a florescent bulb so that it glows, that's the effect of the electrical, not the magnetic field. This effect would occur even if the lines were DC.
The magnetic field couples to loops. If you were to fashion a transformer by looping some Romex around a piece of rebar and connecting the ends to an AC voltmeter, you would see a voltage that would fall as you moved further from the lines. The most common manifestation of the magnetic field in a power line is when they saturate the core of an automobile AM antenna, causing objectionable "static". (FM can be made more immune, it depends on the design.)
The health effects of these fields at the foot of the tower is probably neglible; we drive under power lines all the time. The right of way extents far enough from the lines so that interference with household electronic and electrical devices is not objectionable.
How does your electric toothbrush charge even though there's no metal contact between the toothbrush and the charger stand? 61 & 63 answered well.