Question

A patient is experiencing ventricular fibrillation and the attending doctor delivered a high amount of energy to the patient heart using a square-wave defibrillator. The defibrillator outputs a constant ideal voltage of 1800 V across the electrodes for 5msec, and then the voltage drops to 0 V. If the delivered energy to the patient is 200 J, find the Rtotal (i.e., the total resistance of the setup). Now, compute the energy delivered to the patient when the constant ideal voltage:

drops to 900 V and the duration of the pulse remains 5msec.

Answer 1

To find the total resistance (Rtotal) of the setup, use the formula for energy. The energy delivered to the patient is 200 J. The resistance of the path through the patient is 81 kΩ.

Step-by-step explanation:

To find the total resistance (Rtotal) of the setup, we can use the formula for energy:

Energy (E) = Power (P) x Time (t)

Since we know the voltage (V) and the energy (E), we can find the power using the formula:

Power (P) = Energy (E) / Time (t)

Using the given values, we have:

Power = 200 J / 5 ms = 40 kW

Now, we can use Ohm's Law to find the resistance:

Power (P) = Voltage (V)² / Resistance (R)

40 kW = (1800 V)² / R

R = (1800 V)² / 40 kW = 81 kΩ

To compute the energy delivered to the patient when the constant ideal voltage drops to 900 V, we can use the formula:

Energy (E) = Voltage (V) x Time (t)

Using the given values, we have:

Energy = 900 V x 5 ms = 4.5 kJ