Why Aren't Birds Electrocuted on Powerlines?

  • Thread starter pivoxa15
  • Start date
In summary: The wire is 'bare' to save costs. And the voltages are such that they won't kill you unless you touch them and provide a path to ground, like touching the neutral and a hot wire, or a hot wire and the ground.In summary, birds can perch on high-voltage powerlines without being electrocuted because they are not grounded and therefore do not complete a circuit for current to flow. Additionally, the resistance of birds is high which further limits the current flow. The potential difference between each leg of the bird is also small due to
  • #1
pivoxa15
2,255
1

Homework Statement


Birds are often seen perched on a high-voltage powerline. Why aren't the birds electrocuted?


Homework Equations


V=IR


The Attempt at a Solution


The birds usually have their legs very close together so the potential difference between each leg is small. The resistance of birds are high so I is small according to the equation. But would another factor be that the power line has an insulating material around it which would dramatically decrease V.
 
Physics news on Phys.org
  • #2
You have the right answer for nearly the right reason.

Draw the circuit representing the Bird as a resistor (You could measure resistance across your hand to get a totally non-scientific indication of the birds resistance).
Assume the resistance in the wire is almost nothing.
And then calculate the relative current in each path.

You might want to mention what would happen if a big bird (Stork, Eagle) touched two conductors, or the conductor and the pylon (Assuming it's a metal pylon)?
 
  • #3
In Tango and Cash, Cash says it's because he's not touching the ground :biggrin:
 
  • #4
Cash is right. Since the birds arent touching the ground, the circuit is incomplete.
 
  • #5
The power line is at a high voltage potential, but it is just that - a potential. The bird can perch on the line and come to the same potential voltage as the line with no shock. If there is no complete path from that potential to a higher or lower potential or to ground, no current will flow and the bird will not experience a shock. If you could jump up and grab that power line (without touching anything that would provide a path to ground) you could do the same thing that the bird is doing. Voltage does not hurt you absent current flow.
 
  • #6
"...Birds are often seen perched on a high-voltage powerline..."

Depends on how high is high. While you often see them on power lines rated below 20kV to ground, you'll never see them on the big lines at voltages over 50kV phase to ground. You may see them on the pylons, or grounding wires, but not on the energized conductor wires. I believe their feathers start to rustle in close proximity to thes wires, due to the high voltage gradient, and they don't dare to try getting energized at those voltages ..I believe they'd draw an arc in so doing.
 
  • #7
turbo-1 said:
The power line is at a high voltage potential, but it is just that - a potential. The bird can perch on the line and come to the same potential voltage as the line with no shock. If there is no complete path from that potential to a higher or lower potential or to ground, no current will flow and the bird will not experience a shock. If you could jump up and grab that power line (without touching anything that would provide a path to ground) you could do the same thing that the bird is doing. Voltage does not hurt you absent current flow.

If the potential is high then a small segment of the line (the distance between the feet of the birds) will provide some potential difference. This will mean a current will flow through the bird. Is that correct? Although if we allow V small and R large than V=IR => small I. Is your argument that I in this case is too small to cause the bird harm. Someone dangling on the voltage lines will not cause harm for the same reason although provided their arms are not too widely spaced? Otherwise the potential difference will be larger however R for a human is smaller than a bird.
 
  • #8
Panda said:
You have the right answer for nearly the right reason.

What was wrong with my reason (which was emphasised in the above post)?
 
  • #9
BTW, whacking a powerline with a 15' metal pool-cleaning net doesn't cause electrocution either. I'm just sayin'.
 
  • #10
DaveC426913 said:
BTW, whacking a powerline with a 15' metal pool-cleaning net doesn't cause electrocution either. I'm just sayin'.
Whoaaaa... whacking a power line with a metal net could cause instant death, even if the rod holding the net is non-metal, for it still will have some conducting properties, and allow current to flow through you to the ground. Shoot 170 milliamps through your herat and we'll see you in the next world. Most powerline wires are NOT insulated ...the wire is bare...or the insulation, IF present, is intended only for preventing short circuits due to occasional short duration contacts of small tree branches, and has perhaps only a 600 volt rating. NEVER touch a powerline with ANYTHING.
 
  • #11
Yeah. I honestly don't know why I'm still alive.

BTW, I did not mean to suggest in any way that this was an OK thing to do.
 
  • #12
DaveC426913 said:
Yeah. I honestly don't know why I'm still alive.

BTW, I did not mean to suggest in any way that this was an OK thing to do.

Don't lie, you know you were advocating for global electrocution. I was JUST on my way outside to play russian roulette with the powerlines.

Silly dave, I love you.
 
  • #13
DaveC426913 said:
BTW, whacking a powerline with a 15' metal pool-cleaning net doesn't cause electrocution either. I'm just sayin'.

Try it naked, in a thunderstorm and with a golf club. (Its the golf club that's the biggest risk statistically). Of course, nakedness is not a requirement, it would just really freak the neighbours out.
 
  • #14
pivoxa15 said:
What was wrong with my reason (which was emphasised in the above post)?
I don't see anything wrong with it. The current passing through the bird over that short distance of 'voltage drop' with very low potential difference, coupled with the very low resistance of the wire (something like in the order of one-thousandth of an ohm per foot...I'd have to look it up) would be very low...maybe less than a milliamp or so...an imperceptible and non-deadly current (the 'let-go' current of an adult male human..where the muscles 'freeze'...is about 9 milliamps or so, less for a woman or child (5 or 6 milliamps). But don't assume any insulation on the wires..if they were fully insulated for the applicable phase to ground voltage, that would sure change the picture for the better...but most powerlines use bare wires, at least the high voltage ones.
 
Last edited:
  • #15
I don't see anything wrong with it either... especially the nakedness... hehehe
 
Last edited:
  • #16
"Clothes make the man. Naked people have little or no influence on society."
- Mark Twain
 

FAQ: Why Aren't Birds Electrocuted on Powerlines?

Why don't birds get electrocuted when they sit on power lines?

The reason birds don't get electrocuted when they sit on power lines is because they are not grounded. Power lines are designed to carry electricity at a high voltage but with low current. Since birds are not touching the ground or any other conductive material, the electricity cannot flow through their bodies and they remain unharmed.

Can birds get electrocuted if they touch both a power line and a tree branch?

Yes, it is possible for birds to get electrocuted if they touch both a power line and a tree branch at the same time. This creates a path for electricity to flow through their bodies and can result in injury or death. However, birds have an instinctual understanding of electricity and can usually avoid this type of dangerous situation.

Do birds have a resistance to electricity?

Birds do not have a specific resistance to electricity, but their body composition and size can play a role in their ability to withstand an electric shock. Larger birds, such as eagles, have a higher chance of surviving an electric shock compared to smaller birds like sparrows due to their size and muscle mass.

Are birds immune to electricity?

No, birds are not immune to electricity. In fact, birds can be injured or killed by electricity if they come into contact with high enough voltage or current. However, their survival rate is generally higher compared to other animals due to their unique physiology and behavior around electricity.

Are there any cases of birds being electrocuted on power lines?

While it is rare, there have been documented cases of birds being electrocuted on power lines. This is often due to factors such as wet feathers, a damaged power line, or a bird's inexperience with electricity. Additionally, certain bird species, such as water birds, are more susceptible to electrocution due to their habitat and behavior.

Similar threads

Why can a bird survive on a high voltage power line without getting fried?
Replies
6
Views
2K
Physics E & M Question about a powerline
Replies
5
Views
3K
Why Can Birds Sit Safely on Power Lines but Get Electrocuted When Touching Two?
Replies
3
Views
12K
What Voltage Does a Bird Feel on a Power Line?
Replies
7
Views
2K
Decreasing the resistance at constant voltage
Replies
4
Views
1K
Why do the headlights on the car become dim when the car is starting?
Replies
4
Views
1K
A man was found laying near a powerline
Replies
7
Views
2K
Why doesn’t the motor start right away?
Replies
9
Views
2K
Is the textbook wrong or am I? (circuit with resistors, switches and a battery)
Replies
6
Views
1K
Circuits question, series vs parallel
Replies
5
Views
1K

Hot Threads

Recent Insights

Back
Top