A person with body resistance between his hands of 11 k accidentally grasps the
ID: 1423943 • Letter: A
Question
A person with body resistance between his hands of 11 k accidentally grasps the terminals of a 15-kV power supply.
Part A
If the internal resistance of the power supply is 2200 , what is the current through the person's body?
Express your answer using two significant figures.
Part B
What is the power dissipated in his body?
Express your answer using two significant figures.
Part C
If the power supply is to be made safe by increasing its internal resistance, what should the internal resistance be for the maximum current in the above situation to be Imax=1.00mA or less?
Express your answer using two significant figures.
Explanation / Answer
Internal resistance of the power supply = r = 2200
Body resistance between hands = R = 11k =11000
Power supply voltage = E =15 kV=15000 V
The current through the person's body = i = E / (R+r)
The current through the person's body = i =15000 /13200
(a) The current through the person's body = i =1.1 A
_____________
(b) The power dissipated in his body =i^2R=1.4*104 W
___________________________
If Imax = 1.00 mA =0.001A
R+r=E/Imax
r =E/Imax - R
r = 15000/0.001 - 11000
r =15000000 -11000=14989000
(c) The internal resistance should be14989000 ohm for the maximum current in the above situation to be I(max) = 1.00 mA or less
The internal resistance should be14989000 ohm or 1.5*107 ohm
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