You work for a medical equipment company as an engineer / designer and have been

Question

You work for a medical equipment company as an engineer / designer and have been tasked to design a defibrillator. There are some considerations and practical cacalculations that must be performed piror to building the physical model. You have to specify your design parameters based on figuring out the following information:

a) If the design circuitry is cost effective to build with a power supply output of 300mA of current with a maximum charge capacity of 0.8C, how long would it take to fully charge the if it started with zero charge?

b) What voltage must be supplier to the defibrillator to discharge 3mJ of energy to the patient? Assume that the capacitance of this particular defibrillator is 5pF.

c) You believe a new design concept could deliver a precise current dissipation through a patient's heart with one of the paddles of the defibrillator placed on the patient's back directly behind the heart with the other paddle applied to the chest over the heart (as opposed to the usual method of appling both paddles to the chest). Your design concept requires that your parallel plate capacitor (of the two paddles) discharge through a dielectric, in this case, water in the human body (k = 80). Assuming that the diamter of your circular paddles is 15cm and the chest to back distance for average patient is 30cm, calculate the capacitance of your defibrillator

Explanation / Answer

part A:

current I = charge Q/time

so

time t = Q/i

t = 0.8/300 e -3

t = 2.67 secs

-----------------------------------

B. eenrgy U = 0.5 CV^2

V^2 = 2U/C

V^2 = 2 * 3 e-3/(5 e-12)

V = 36.4 K Volts

-----------------------------------------------------------

c.
Remember and apply for parallel plate caapcitor, these as formulas

1. Capacitance C = K eoA/d   

where K is dieelctric constant ( for air K = 1)

eo is permnittivity constant = 8.85 e-12

A is area = pi^2 ( for circular plates) and l* b for rectanular plates

and

d is the distance between the plates

so C = 80 * 8.85 e -12* 3.14* 0.075* 0.075/0.3

C = 41.67 pF

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.