Why Don’t Birds Sitting On Wires Get Electrocuted?

The reason birds don’t get electrocuted when sitting on power lines is because they are not completing the circuit that is required for electricity to flow. If a bird were to have one foot on the wire and the other foot on the ground or a different wire, the bird would be electrocuted because it would be acting as a conducting medium.

Characters in the movies often end up with a blackened face and frizzy hair after coming in contact with a live wire charged with electricity. As observers, we laugh our hearts out at these ridiculous moments, but in real life, a live wire won’t be so gentle. You’d end up with more than just frizzy hair, torn clothes, and a crooked face. The thousands of volts could kill you instantaneously – unless you’re a bird, that is.

It’s a very common sight to see birds perched on top of electric wires, almost mocking us with their ability to relax at such heights. Birds have no problem sitting, undisturbed, on the high voltage wires lining the roads, but it has nothing to do with them being birds. As you’ve probably also seen, squirrels can run along wires unscathed too!

So What’s The Explanation?

This is all due to the connections that they’re making, or rather, not making.

Electric current is simply the movement of electrons. For electrons to move from one point to another, they require an adequate potential difference between the two points.

Just like all types of energy, electricity pursues equilibrium (or balance). This means that electricity will flow from areas of high energy to low energy along the path of least resistance. For example, if the bird were to have one foot on the wire they’re standing on, and the other foot on the ground or a different wire with less voltage, the bird would be electrocuted. This is because the bird would be acting as a conducting medium that allows the electric current to pass from the high voltage substance (wire) to the low voltage substance (ground).

When a bird is sitting happily on top of a wire:

(1) The circuit is incomplete, so the flow of electrons required to conduct electricity is hindered.

(2) The potential difference between all points on the wire is zero

Similarly, if a person were to stand on top of a power line, he would also remain unaffected by the wire (the wire wouldn’t be able to sustain the person’s weight, which is why this is purely hypothetical). A person standing on the ground, however, completes the circuit, so the person is electrocuted when coming in contact with the wire.

If The Wires Are So Dangerous, How Do Workers Carry Out Maintenance Work?

Workers on power lines use strong insulating materials in their clothing, equipment, and bucket trucks. Insulating materials, such as rubber and asbestos, are materials through which electricity struggles to flow. Therefore, instead of passing through the worker, the electrons stay on the other side of his rubber gloves or rubber-handled tools.

Another technique when working on power lines is to hang beneath a helicopter. Since neither the worker nor the helicopter is connected to the ground (like those birds), the worker just has to make sure that he only touches one wire at a time.

Despite taking such precautions, electrical maintenance is one of the most dangerous jobs out there. Therefore, it’s probably a wise choice to just stay away from electrical wires unless you’re a trained professional… or a bird.

Why Does A High Voltage Wire Make A Noise?

As you know, high voltage lines consist of 2 wires that pass current. These wires create a magnetic field on top of each other, and these magnetic fields cause a magnetic force to act on the wires. Since the current passing is alternating, that is, it is variable, this force also changes constantly with the current. This variable force causes the wires to oscillate. Here is the buzz we hear from the oscillation of the strings.

It is based on alternating current. Alternating current varies according to the sine function (sine wave). So the main reason for this is the famous trigonometric function in mathematics, the sine function.

I call it sine sound.

i=imax.sin(ωt).�=����.sin⁡(ω�).

sound extractor devices work with different types of current. however, each sound has its own current wave. For example, the headphones you listen to music generate current waves according to the type of music and this electric current turns into sound. We often call it a loudspeaker. Let the function of the electric current of a music be expressed as M(x)�(�). Suppose there is a dam that generates electricity according to the function of this music. According to this assumption, high voltage lines will also make the sounds of that music. so strange noises would come from the electric poles. we would probably hear the electric poles singing.

In that case, if we run a speaker directly with alternating current, zzzzzz or rrrrrrr sounds will come from this speaker. This is the sound of the sine function. On the other hand, if we operate this speaker with battery, we will hear sssss sound or space sound. We know that batteries produce a straight/constant current. I am not a physicist and have not experimented with this. I just made these comments by taking advantage of the power of mathematics. Maybe i'm wrong, but I'll test this at home.

As seen in the image, you see electrical current waves of any music. Now how do we find the function that represents this? If we use the Newton interpolation method, we will not be very successful. Maybe we can do some approximation to this function. These waves you see are not regular like alternating current and constant current.

There is also the aspect of this that has to do with the light intensity. Take a good look at the lamp you see in your home. you will see the sine function there too.

I was very small indeed. I saw a lamp connected to the speaker and the power of the lamp was blinking according to the intensity of the sound. The lamp glowed brighter when the man shouted into the microphone, and turned off when the man was silent. What was that mysterious thing?That's when i realized that strange things happen in life.

Transient Heat Transfer

Thanks To

Pratik

What is Transient heat transfer?

The type of heat transfer in which, the temperature of the body changes with respect to time is known as transient heat transfer.

It is also known as the Unsteady-state heat transfer.

Therefore for transient heat transfer,

$\frac{dt}{\partial \tau }$ ≠ 0

Where,
dt = Change in temperature
d𝜏 = Time interval

In transient heat conduction, the temperature and rate of heat flow at a point change continuously with respect to time.

Transient heat transfer examples:

In real conditions, the heat transfer mostly takes place in a transient way. Here are some examples of transient heat transfer.

1. Heating or cooling of the engines.
2. Heat transfer in buildings in day.
3. Cooling or heating of foods.
4. Heating of metal bar.

When the rate of heat energy entering into the body does not match with the rate of heat leaving the body, then the internal energy of the body increases or decreases, and therefore the temperature of the body increases with respect to time.

That is, $Q_{\text{in}}$ ≠ $Q_{Out}$

$\Delta E$ ≠ 0

$\frac{dt}{\partial \tau }$ ≠ 0

Therefore this situation is known as Transient or Unsteady state heat transfer.

Different cases of Transient heat transfer:

Case 1:-

When one end of the object is subjected to a heat source and another end is in contact with a sink with no internal heat generation and If $Q_{\text{in}}>Q_{Out}$

Then heat gained by body is positive.

$\Delta E$ = +ve

Hence $\frac{dt}{\partial \tau }$ = +ve

Therefore it is the case of Transient heat transfer.

Case 2:-

When $Q_{\text{in}}<Q_{Out}$and $Q_{\text{generation}}=0$, then the energy of the body is lowered.

$\Delta E$ = -ve

Hence $\frac{dt}{\partial \tau }$ = -ve

It is also case of Transient heat transfer.

Case 3:-

When the object is completely surrounded by the source.

In this case $Q_{Out}$= 0 and $Q_{\text{in}}$ = +ve

Therefore the internal energy of the object continuously increases.

$\Delta E$ = +ve

Hence $\frac{dt}{\partial \tau }$ = +ve

It is Transient heat transfer.

Example:- Heating of metal bar in the furnace.

Case 4:-

When the object is completely surrounded by the low-temperature sink.

In this case, heat is lost by the object.

Hence $Q_{\text{in}}$ = 0 and $Q_{\text{out}}$

Therefore the internal energy of the object is continuously decreasing.

$\Delta E$ = -ve

Hence $\frac{dt}{\partial \tau }$ = -ve

In this case, the temperature of the body decreases with respect to time and it is also the case of transient heat transfer.

Biot number:

The biot number represents the distribution of temperature within the body.

Biot number is defined as the ratio of conductive resistance of the body to the convective resistance on the surface of the body.

Mathematically it is given by,

Bi = $\frac{\text{Internal conductive resistance}}{\text{External convective resistance}}$

Bi = $\frac{\frac{L_C}{K.A}}{\frac{1}{hA}}$ = $\frac{h{L}_C}{K}$

Bi = $\frac{h{L}_C}{K}$

The lower value for the biot number indicates that the object has less conductive resistance in comparison with convective resistance therefore the value of the temperature gradient is less.

If the value of the Biot number is higher, then the object has comparatively higher conductive resistance in comparison with convective resistance, and in this case, the value of the temperature gradient is higher.

The following figure shows the temperature distribution in the body for both these conditions.

Methods to solve transient heat transfer:

1] Lumped system analysis:-

The lumped system analysis method is used when the value of the biot number is less than 0.1.

In this case, the conductive resistance of the object is considered negligible. It means that the material has very high thermal conductivity.

The temperature distribution in such conditions is considered uniform throughout the body (The temperature of the body is constant).

The relation for lumped capacity method is given by,

$\frac{t-t_{\infty }}{t_1-t_{\infty }}$= $e^{-\left\{\frac{h.A}{\rho .V.C}\right\}}$ When Bi < 0.1

Where,
t = Temperature of object after of 𝜏
$t_{\infty }$=Atmospheric temperature
$t_1$ = Initial temperatre of object at 𝜏=0
As = Surface area of object
ρ = Density of object
V = Volume of object
C = Specific heat of object
h = Convective heat transfer coefficient of medium
𝜏 = Time to reach temperature of object from initial temperature to final temperature

2] Heisler chart:-

Heisler chart is the graphical method to analyze transient heat conduction system

The Heisler chart method is used when 0.1 < Bi < 100

The Heisler chart is different for infinite long plane wall, cylinder, and sphere.