Because human tissue is a fairly good conductor of electricity, current passing
ID: 1534337 • Letter: B
Question
Because human tissue is a fairly good conductor of electricity, current passing through it can be dangerous. In fact, sustained current as small as 25 mu A passing through the heart can be fatal. Suppose a patient is undergoing open-heart surgery. Assume that the heart has a constant resistance of 250 Ohm. Determine the minimum voltage that poses a danger to the patient SET UP AND SOLVE shows our sketch. We know that 1 mu A = 1 times 10^-6 A. We use Ohm's law to relate voltage, resistance, and current: V = IR = (25 times 10^-6 A) (250 Ohm) = 6.25 times 10^-3 V = 6.25 mV REFLECT Our result shows that even a small voltage can be dangerous if applied directly to the heart. As a safety measure, any electrical equipment near a patient during surgery must be "grounded." Grounding means that there is a low-resistance conducting path to the earth, so any undesirable current will pass into the ground instead of through the person. During some surgeries, even the patient is grounded to prevent electric shock. A voltage of 9.00V across the terminals of a device produces a current of 3.00 mA through the device. What is the resistance of the device? Express your answer in kilo ohms to three significant figures.Explanation / Answer
Resistance = R
Voltage = V
Current = I
according to ohm's law V = IR
=> R = V / I
=> = 9 / 3 * 10-3 = 3 kohm