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Explain why birds can sit on power lines safely, whereas leaning a metal ladder up against a power line to fetch a stuck kite is extremely dangerous.
The reason why it is safe for the birds to sit on the power lines, but leaning a metal ladder against a power line is extremely dangerous.
Answer to Problem 1Q
The resistance of the bird is larger compared to the resistance of the wire between the bird’s feet, so that a very little current passes through the bird as it sits on the power line.
A metal ladder leaned against a power line will have a direct contact between the high potential line and ground which implies person standing on the ladder will have a larger potential difference between his hand and feet which produces large current through the person’s body large enough to cause substantial damage.
Explanation of Solution
Even though the bird’s feet are at high potential compared to the ground, the potential difference between the feet of the bird is very little since they are close together on the wire. And also the resistance of the bird is much greater when compared to the resistance of the wire between the bird’s feet. These two resistance are in parallel so that only a very little current will pass through the bird when it sits on the transmission line.
A metal ladder leaned against a power line will have a direct contact to the high potential line and ground so that the person standing on the ladder will have a larger potential difference between his hand and feet.
Even if the person’s resistance is large, the potential difference will also be so large to produce current through the person’s body large enough to cause severe damage or death.
Therefore, it is safe for the birds to sit on the power lines, but leaning a metal ladder against a power line is extremely dangerous.
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