Physics
19.10.2022 12:13
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Birds resting on high-voltage power lines are a common sight. the copper wire on

Birds resting on high-voltage power lines are a common sight. the copper wire on which a bird stands is 1.28 cm in diameter and carries a current of 149

a. if the bird's feet are 4.12 cm apart, what is the potential difference across its body? copper's resistivity is 1.68 × 10−8 ω m . answer in units of µv.
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djfluffyman999
djfluffyman999
4,4(55 marks)

8\cdot 10^{-4} V

Explanation:

First of all, let's find the cross-sectional area of the copper wire. The radius of the wire half the diameter:

r=\frac{d}{2}=\frac{1.28 cm}{2}=0.64 cm=6.4\cdot 10^{-3} m

So the area is

A=\pi r^2 = \pi (6.4\cdot 10^{-3} m)^2=1.29\cdot 10^{-4} m^2

Now we can calculate the resistance of the piece of copper wire between the bird's feet, with the formula:

R=\rho \frac{L}{A}

where

\rho=1.68\cdot 10^{-8} \Omega m is the resistivity of copper

L=4.12 cm=4.12 \cdot 10^{-2} m is the length of the piece of wire

A=1.29\cdot 10^{-4} m^2 is the cross-sectional area

Substituting, we find

R=(1.68\cdot 10^{-8} m^2)\frac{4.12\cdot 10^{-2} m}{1.29\cdot 10^{-4} m^2}=5.4\cdot 10^{-6} \Omega

And since we know the current in the wire, I=149 A, we can now find the potential difference across the body of the bird, by using Ohm's law:

V=IR=(149 A)(5.4\cdot 10^{-6} \Omega)=8\cdot 10^{-4} V

leenzazou587
leenzazou587
4,7(27 marks)
Distance between Metro  transit station to Whitstleville = 14 miles
Average speed of train = 35 mph
Time of departure from metro = 10.00 AM
Time to the next station, t= d/s = 14/35 = 0.4 hrs = 24 minutes
Since it takes 5 minutes to the station, the traveler leaves the apartment at,

10.00 AM + (24-5 minutes) = 10.19 AM

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