1. A bird is sitting on an uninsulated power line carrying 1000A. We know the fo

Question

1. A bird is sitting on an uninsulated power line carrying 1000A. We know the following information: a) The ACSR (aluminum conductor steel reinforced) cable is 1.00 inch in diameter, with a steel core of 0.50 inches in diameter. Consider only the aluminum as conducting the current. b) This aluminum has a resistivity of 2.82x108 Ohm-meters. c) The bird's feet are 1.25 inches apart d) The internal resistance of the bird from foot to foot is 100. Determine the following: 1.1) What is the resistance of the cable between the feet of the bird? 1.2) How much current is flowing through the bird? 1.3) How many electrons per second is flowing through the bird? 1.4) If 5mA is able to cause death, will the bird survive? 2. You fell from a rock overhang but managed to grab hold of the power line the bird in problem 1 was sitting on. You scared the bird and it flew away. You know the following information: a) Your hands are 16" apart on the cable. b) Your resistance from sweaty hand to hand is 500. Determine the following: 2.1) What is the resistance of the cable between your hands? 2.2) How much current will flow across your heart? 2.3) How many electrons per second is that current? 2.4) If 30mA is able to cause your heart to start fibrillating, leading to death by electrocution, should you let go and fall (only breaking a leg), or hang on for help to arrive. 2.5) Is there anything else you could do to increase survivability?

Explanation / Answer

1.1) distance between feets=1.25 inches

=1.25 * 2.45 cm

=1.25 * 2.45 * 10-2 m

resistivity is given as = 2.82 * 10-8 ohm meter

   so resistance between feets = 1.25 * 2.45 * 10-2 * 2.82 * 10-8

   = 8.63625 * 10-10 ohm

1.2)

inernal resistance of the bird is 100 ohm given

now 100 ohm and  8.63625 * 10-10 ohm are in paralle,,,,,,so current divides in parallel

according to current division rule current in 100 ohm restor i.e bird

= (total current of cable *  8.63625 * 10-10) / ( 8.63625 * 10-10 + 100)

=(1000 *  8.63625 * 10-10) / ( 8.63625 * 10-10 + 100)

=8.63625 * 10-9 A

=8.63625 nA

1.3) electrons per second is nothing but current flowing................

q/t = i

q= i *t =8.63625 * 10-9 electrons flowing per second

1.4) 5 mA causes death ....here only nano amps of current is there so there is no death caused............

2.1)

distance between hands =16 inches

=16 * 2.45 cm

=16 * 2.45 * 10-2 m

resistivity is given as = 2.82 * 10-8 ohm meter

   so resistance between hands = 16 * 2.45 * 10-2 * 2.82 * 10-8

   =110.544 *10-10 ohm

2.2)

  inernal resistance of the body is 500 ohm given

now 500 ohm and  110.544 *10-10 ohm are in paralle,,,,,,so current divides in parallel

according to current division rule current in 500 ohm restor i.e body

= (total current of cable *  110.544 *10-10 ) / ( 110.544 *10-10 + 500)

= (1000 *  110.544 *10-10) / ( 110.544 *10-10 + 500)

= 221.088* 10-10 A

= 22.1088 nA

2.3)

electrons per second is nothing but current flowing................

q/t = i

q= i *t =221.088* 10-10 electrons flowing per second

2.4) 30 mA causes death ....here only nano amps of current is there so there is no death caused............

2.5) even there in no severe current flow through body....at fingers there may be chance of circulating currents

inside finger so it is better to fall on earth.....

     

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