If you touch the two terminals of a power supply with your two fingertips on opp
ID: 1443015 • Letter: I
Question
If you touch the two terminals of a power supply with your two fingertips on opposite hands, the potential difference will produce a current through your torso. The maximum safe current is approximately 5 mA.
(a) If your hands are completely dry, the resistance of your body from fingertip to fingertip is approximately 535 k. If you accidentally touch both terminals of your 120 V household electricity supply with dry fingers, what current will flow, and will you receive a dangerous shock in mA?
(b) If your hands are moist, your resistance drops to approximately 1.2 k. If you accidentally touch both terminals of your120 V household supply with moist fingers, what current will flow in mA, and will you receive a dangerous shock?
Explanation / Answer
a) I = V/R = 120 / (535 x 10^3)
I = 0.224 x 10^-3 A = 0.224 mA
this less than 5 mA hence it is safe.
b) I = (120) / (1.2 x 10^3) = 0.1 A
which way more than 5 mA.
hence you will get dangerous shock,