You may often see birds sitting on a wire, but have you ever thought that why the current flowing from the wires is not harmful to these birds on a wire. Maybe you think about it but do not get an appropriate answer for it. So, Today we will tell you.
Why don't the birds sitting on the wire feel the current?
The answer to this question is that the current flows in a loop, which means the circuit is closed. The Bird sitting on a single wire doesn't complete the circuit. As the circuit is not complete so the current does not pass through the bird. This is not true. In short, the bird's resistance is higher than the wire between the bird's legs, so it passes through the wire instead of passing through the bird.
You take a wire and connect the ends to a twenty-volt battery. The wire must have some resistance. When the bird sits on that wire, it must have some resistance too. The bird and the wire between the bird's legs have two parallel resistors. In which the resistance of the bird is much higher than that of the wire.
We read in electronics that when two resistors are parallel, the voltage across both is the same. According to Ohm's law
V = IR
I = V / R
Since we have the same voltage, the current and resistance ratios will be inversely proportional.
I α 1 / R
This means that the higher the resistance of the resistor, the less current will pass through it, and the lower the resistance the high amount of current will pass through the wire.
In this way, less current will pass through the bird than through the wire.
How birds can feel current?
When one foot of the bird is placed near one end of the battery and the other one is placed near the other end, the length of the wire between the bird's legs increases. Thus the resistance of the wire is much less than that of the bird and the current will pass through the bird and the bird will die and may be able to see different colors of Moon and stars in the daytime 😁.
The same thing happens with birds sitting on electric wires outside. When the bird touches both wires, instead of the current going forward and enduring so much resistance of the wire, it passes through the bird and the bird dies. So when someone is hit by electric shock we say that there is a shock of so many volts. That is not to say that there was a shock of so many amperes.
Let's understand it more extensively.
When two resistors are placed in parallel in any circuit, by definition the potential difference at both ends is equal - but the current in them may be different because the amount of current in the resistor is determined by dividing the potential difference by resistance.
When a bird sits on a wire, there will be some resistance of the wire (which is only a few centimeters long) between its legs. Suppose this resistance is one-tenth of an ohm, that is, ten milliohms Just Imagine the current flowing from one foot to its body and the current going back from the other foot. The body of a bird can also be supposed as a resistor. Suppose this resistance is 100 ohms. Suppose a 10-ampere current is flowing from a wire. so the potential difference between the two legs of the bird at the resistance of the wire (which is one ohm) is 100 millivolts - this means that there is also a potential difference of 100 millivolts at the resistance of the bird's body. Since the resistance of this bird is 100 ohms, the amount of current passing through the body of the bird will be one milliampere - ie 10 amperes of current passing through the wire so only 1 milliampere current will pass through the body of the bird which will not cause any harm to the bird.
I have given this example just to illustrate the resistance of the wire will be many times less than ten milliohms and the same proportion of less current will pass through the body of the bird - so sitting on the wire for the birds. Not is harmful
The voltage drop across a few centimeter long piece of wire is so small that in normal calculations the losses in the wire are ignored and it is assumed that the bird's two feet are at the same potential.
Also check: What happens if the Sun Suddenly Disappears?
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