If you touch the two terminals of a power supply with your two fingertips on opp

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 450 k ohm. If you accidentally touch both terminals of your 125 V household electricity supply with dry fingers, what current will flow, and will you receive a dangerous shock? (b) If your hands are moist, your resistance drops to approximately 1.3 k ohm. If you accidentally touch both terminals of your 125 V household supply with moist fingers, what current will flow, and will you receive a dangerous shock? (c) For the situation of part a, what electric power is dissipated in your body? Would you notice the heating? Yes No

Explanation / Answer

Part A)

V = IR

125 = I(450000)

I = 2.78 X 10-4 Amps

That is .278 mA - Much less than 5 mA, so you are safe

Part B)

V = IR

125 = I(1300)

I = .0962 Amps

That is 96.2 mA - Much higher than 5 mA, so you are unsafe

Part C)

P = IV

P = (2.78 X 10-4)(125)

P = .0348 Watts

That is 34.8 mW

No, you won't notice any body heating.

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