# Re: [SI-LIST] : Hi SI-gurus,One stupid question

From: Bob Lewandowski ([email protected])
Date: Wed Mar 08 2000 - 18:07:04 PST

For a single wire, near ground: (parallel to ground, where d = wire diameter, and h = height of wire above ground)

For d << h,

Z0=(138/(SQRT(Epislon R))) *LOG10(4*h/d)

---Bob Lewandowski
Vixel Corp.

opams cybernetics wrote:

> Hi SI-gurus,
>
> One stupid question:
>
> Take a long (say 10 ft) long rod of perfect conductor (say copper) and
> connect one of its end to the +ve terminal of a battery through a
> switch. The other end of the battery is grounded to the earth.
>
> Now this rod should behave as a transmission line when you quickly close
> the swich, right? How do you calculate the impedance of this line? Does
> this mean that the impedance will be different when you put the rod
> parallel the the earth and when put perpendicular to the earth (because
> the distance from the earth and hence capacitance to the ground is
> different)?
>
> Sorry for this silly question.
>
> Opamps
>
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