Electrical hazards to tree workers around bucket trucks.

[steve_bank]

Energy and work are equivalebt. Energy is described as the caoacity to do work. Work is force x distance.

Lift a rock in your and hold it stedy. You have increased gravutaional potential energy. The amount of work you can do by letting the rock fall is proportional to potential energy difference between the rock in hand and the rock on ground.

Potential in this case means the potential of doing work.

A battery has a potential difference between the two terminals. Moving electrons is work, force x distance. The battery represents a potential difference. It should be possible to express the voltage potential and gravitational potential in the same units. I'd have to look at the SI dimensions for voltage.

So you could say 'That battery over there has got some greal potential to make something happen!'

 

[fast]

Makes sense.

I say to the both of ya

 

[Derec]

What I’m left thinking is that potential energy is not in fact a kind of energy at all—or at least not a type of energy.

Oh, it most certainly is. The term "potential" distinguishes it from kinetic energy, energy of motion. There are different kinds of potential energy. Take bow and arrow. To draw a string you have to do work (force times distance, as long as they are in the same direction). The potential energy of ATP in your muscles is converted to kinetic energy of your arm and the bow which is converted to elastic potential energy of a bow under tension. When you release the string, all that potential energy is converted to kinetic energy of the bow but also of the arrow real fast (generating much more power than you had to sustain during the drawing) and the arrow flies away really fast.
First Law of Thermodynamics says you can't create or destroy energy, but you merely convert it from one form to another and one system to another. Two ways to transfer energy are work and heat.

One more remark about potential vs. potential energy. They are related, but not the same. Electrical potential (with potential difference being the voltage) is measured in Volts, energy in Joules. Potential is just potential energy per unit charge. So if you multiply voltage by charge in the system, that gives you the electrical energy contained in it.

If one says x has energy, then if the only energy one can point to that x has is potential energy, then one was incorrect to begin with to say x has energy. That would be like saying risk of harm is a type of harm.

The "potential" in potential energy is not that it is potentially energy, but that it has the potential to do work and cause motion and be converted to kinetic energy.

There is no energy UNTIL the circuit is completed.

No. See First Law of Thermodynamics.
One has to expend energy, through work, to separate charges to create a potential difference. That energy is not gone.

 

[Treedbear]

I think you're over-complicating this. Changing potential causes current flow. When the truck touches the power line it acquires electrical charge. That means a momentary current flow. And a very tiny current flow can be used to detect that charge.

It would be momentary in DC, but this is AC, so the truck would be changing from positively to negatively charged 60 times each second, so a little current would be flowing in and out all the time.

Say, that's right! No direct connection required. Just a insulated metal plate mounted on the bottom of the truck and connected to the chassis by a wire and a sensitive AC ammeter.

 

[bilby]

I think you're over-complicating this. Changing potential causes current flow. When the truck touches the power line it acquires electrical charge. That means a momentary current flow. And a very tiny current flow can be used to detect that charge.

It would be momentary in DC, but this is AC, so the truck would be changing from positively to negatively charged 60 times each second, so a little current would be flowing in and out all the time.

Say, that's right! No direct connection required. Just a insulated metal plate mounted on the bottom of the truck and connected to the chassis by a wire and a sensitive AC ammeter.

It's still likely cheaper, and certainly safer, to just electrically isolate the bucket and arm from the truck.

Eliminating a hazard is always preferable to detecting and warning about it.

And in real world situations, if the detector isn't correctly maintained and protected from damage (and I have seen how gentle tree-loppers are with their equipment, and seriously doubt that it will be), a detector can actually increase the risk. If people expect a warning in the event of the truck becoming energised, they are less likely to be cautious - but the absence of an alarm could either mean 'everything is safe', OR it could mean 'the alarm no longer works'.

 

[steve_bank]

Wall scanners that find metal and live wires have been around for a while. Isolation of a metal lift arm would be a challenge. The lift arm could be made of composites. Henry Ford made a car out of a hemp composite material that was strong. Hemp was outlawed after WWII. I like the idea of a flexible rubber sheath. Cheap and easy to retrofit.

https://www.homedepot.com/p/Bosch-D...for-Wood-Metal-and-AC-Wiring-GMS120/202850662

 

[bilby]

Wall scanners that find metal and live wires have been around for a while. Isolation of a metal lift arm would be a challenge. The lift arm could be made of composites. Henry Ford made a car out of a hemp composite material that was strong. Hemp was outlawed after WWII. I like the idea of a flexible rubber sheath. Cheap and easy to retrofit.

https://www.homedepot.com/p/Bosch-D...for-Wood-Metal-and-AC-Wiring-GMS120/202850662

Electrically isolated lift arms are a commonplace around here, so it's obviously not very much of a challenge.