Car capacitance
 

For those who are interested in the numbers, the
capacity between two cars is somewhere around 1000 pf
car-to-car.

Which means that any one car to ground is probably
something like 2000 pf or thereabouts.

Jim


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"jim rozen" wrote: (clip) capacity between two cars is somewhere around 1000
pf car-to-car.(clip)
^^^^^^^^^^^^^
Interesting fact, Jim, but where will I get a chance to use it? :-) Also,
since capacitance is dependent on the distance between the "plates" (cars),
what is the distance at which this figure is correct? Please respond soon,
in case I have to know. BG

"jim rozen" wrote in message
...
For those who are interested in the numbers, the
capacity between two cars is somewhere around 1000 pf
car-to-car.

Which means that any one car to ground is probably
something like 2000 pf or thereabouts.

Jim

Jim

Are the cars far enough apart that their car to car capacitance is
negligable?

Jerry

In article i7KUd.45251$EL5.43141@trnddc05, Jerry Martes says...

Are the cars far enough apart that their car to car capacitance is
negligable?

They were 10 feet apart.

Jim


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Jim,

Does this mean 1000 pf is the capacitance of two cars very close together
with each forming one plate of a capacitor?

Bob (tired of the antenna thing) Swinney
"jim rozen" wrote in message
...
For those who are interested in the numbers, the
capacity between two cars is somewhere around 1000 pf
car-to-car.

Which means that any one car to ground is probably
something like 2000 pf or thereabouts.

Jim


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In article , Robert Swinney says...

Jim,

Does this mean 1000 pf is the capacitance of two cars very close together
with each forming one plate of a capacitor?

With the earth in between. The implication is that
one car to ground is about 2000 pf. This is within
a factor of two from a simply calculated value, with
10 cm being the separation, and 10 sq M of plate area.

What this says is that at 1 MHz, the car body is coupled
to the ground via an approximately 80 ohm resistor. This
is large enough that there could be significant rf voltages
developed on the exterior of the car body at that frequency.

It implies that Jerry's suggestion (at am frequencies
the whip may be an electrostatic probe to measure the
body voltage) is indeed plausible.

Jim


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On 28 Feb 2005 11:23:42 -0800, jim rozen
wrote:

In article i7KUd.45251$EL5.43141@trnddc05, Jerry Martes says...

Are the cars far enough apart that their car to car capacitance is
negligable?

They were 10 feet apart.

Jim

What was the relative humidity?

Gunner

It's better to be a red person in a blue state
than a blue person in a red state. As a red
person, if your blue neighbors turn into a mob
at least you have a gun to protect yourself.
As a blue person, your only hope is to appease
the red mob with herbal tea and marinated tofu.

(Phil Garding)

On 28 Feb 2005 10:04:55 -0800, jim rozen wrote:

For those who are interested in the numbers, the
capacity between two cars is somewhere around 1000 pf
car-to-car.

Which means that any one car to ground is probably
something like 2000 pf or thereabouts.

Jim


Have you tried the new 'green' electrolytic cars?


Mark Rand
RTFM

On 28 Feb 2005 13:25:02 -0800, jim rozen
wrote:

In article , Robert Swinney says...

Jim,

Does this mean 1000 pf is the capacitance of two cars very close together
with each forming one plate of a capacitor?

With the earth in between. The implication is that
one car to ground is about 2000 pf. This is within
a factor of two from a simply calculated value, with
10 cm being the separation, and 10 sq M of plate area.

What this says is that at 1 MHz, the car body is coupled
to the ground via an approximately 80 ohm resistor. This
is large enough that there could be significant rf voltages
developed on the exterior of the car body at that frequency.

It implies that Jerry's suggestion (at am frequencies
the whip may be an electrostatic probe to measure the
body voltage) is indeed plausible.

Jim
Jim,
I have found the capacitance between cars to increase with the
distance. In fact, with the cars 6 inches the capacitance is zero.
Unless you use real skinny people. Then the capacitance rises with the
length of the cars.
ERS

jim rozen wrote:
For those who are interested in the numbers, the
capacity between two cars is somewhere around 1000 pf
car-to-car.

Which means that any one car to ground is probably
something like 2000 pf or thereabouts.

Jim


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jim rozen wrote:
For those who are interested in the numbers, the
capacity between two cars is somewhere around 1000 pf
car-to-car.

Which means that any one car to ground is probably
something like 2000 pf or thereabouts.

Jim


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Back in the good old days we used to charge our cars up with a model T
spark coil and a groundwire. Until the charge wore off, anyone touching
a door handle would get quite a jolt.
Engineman1

In article , Gunner says...

On 28 Feb 2005 11:23:42 -0800, jim rozen
wrote:

In article i7KUd.45251$EL5.43141@trnddc05, Jerry Martes says...

Are the cars far enough apart that their car to car capacitance is
negligable?

They were 10 feet apart.

Jim

What was the relative humidity?

Gunner

It's better to be a red person in a blue state
than a blue person in a red state. As a red
person, if your blue neighbors turn into a mob
at least you have a gun to protect yourself.
As a blue person, your only hope is to appease
the red mob with herbal tea and marinated tofu.

(Phil Garding)


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In article , Gunner says...

What was the relative humidity?

Hmm. It was last night when I did it - my guess was it was around
20 percent. But only a guess there. Clear night, cold, around
25F.

Jim


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On 28 Feb 2005 10:04:55 -0800, jim rozen
wrote:

For those who are interested in the numbers, the
capacity between two cars is somewhere around 1000 pf
car-to-car.

Which means that any one car to ground is probably
something like 2000 pf or thereabouts.

Jim


Is that free air capaciatance or using an oil dielectric?

If using an oil dielectric have you noticed any variation in changing
from 10W-40 to 5W-50??

Enquiring minds want to know-

H.

On 28 Feb 2005 10:04:55 -0800, jim rozen
wrote:

For those who are interested in the numbers, the
capacity between two cars is somewhere around 1000 pf
car-to-car.

Which means that any one car to ground is probably
something like 2000 pf or thereabouts.

I sure blew that estimate! There's no substitute for real data,
thanks for doing the measurement.

On 28 Feb 2005 13:25:02 -0800, jim rozen
wrote:

In article , Robert Swinney says...

Jim,

Does this mean 1000 pf is the capacitance of two cars very close together
with each forming one plate of a capacitor?

With the earth in between. The implication is that
one car to ground is about 2000 pf. This is within
a factor of two from a simply calculated value, with
10 cm being the separation, and 10 sq M of plate area.

What this says is that at 1 MHz, the car body is coupled
to the ground via an approximately 80 ohm resistor.

Reactance rather than resistance. You knew that!

In article , Don Foreman says...

What this says is that at 1 MHz, the car body is coupled
to the ground via an approximately 80 ohm resistor.

Reactance rather than resistance. You knew that!

For this particular forum, "resistance" conveys
the best concept. Those who understand the difference,
undestand why I used that term. g

Jim


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