68) If you touch the two terminals of a power supply with your two finger tips o
ID: 1590371 • Letter: 6
Question
68) If you touch the two terminals of a power supply with your two finger tips of opposite hands, the potential diffrence will produce a current through your torso. The maximum safe current is approximately 5mA.
A) If your hands are completely dry, the resistance of your body from fingertip to fingertip is approximately 500 kohm. If you accidentally touch both terminals of your 120 V household electricity supply with dry fingertips, will you receive a dangerous shock?
B) If your hands are moist, your resistance drops to approximately 1kohm. If you accidently touch both terminals of your 120V household supply with moist fingers, will you receive a dangerous shock?
Explanation / Answer
A)
Potential difference , V = 120
R = resistance = 500,000 ohm
current using ohm's law is given as
i = V/R = 120 / 500,000 = 0.00024 A
the current is below the safe limit of 0.005 A , hence it will not be dangerous
B(
Potential difference , V = 120
R = resistance = 1000 ohm
current using ohm's law is given as
i = V/R = 120 / 1,000 = 0.12 A
it is above the safe limit , hence there will be a shock
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