Question 3: (5 points) An important technical ap- plication of capacitors delive

Question

Question 3: (5 points) An important technical ap- plication of capacitors delivers timed electrical shocks to the heart muscle, to stimulate its proper contraction. This circuit shows - in a very simplified way - how it works: First, with the switch kept open, the capacitor is charged by the battery. When the switch is closed, the capacitor dis- charges through the heart, represented by Ro. The opening and closing of the switch is controlled by an other circuit not shown here, while the capacitor and resistor R1 of this circuit are responsible for charging and delivery of electrical stimulation to the heart. is a pacemaker, a device that Voat Ro a) Suppose the capacitor has been discharged and then the switch is opened. In the figure, draw arrows by each wire of the circuit, indicating the direction of the current flow when the capacitor is being charged. If there is no current flow through a particular wire when the switch is first opened, write "I-0 b) Write down the time constant Tcharge for the charging process, in terms of C, Ri and Ro. Explain your reasoning briefly. c) When the charging has finished, what is the voltage across the capacitor? Explain your answer d) Indicate the sign of the charge on each capacitor plate.

Explanation / Answer

a] current in R1 is from left to right, current in wire having C is also from left to right(clockwise). Current in wire having swich is zero.

b] Time constant Tcharge = [R1 + Rheart]*C because the two resistances will be in series, so equivalent resistance is sum of both.

c] voltage = Vbat. because there will be no voltage across resistors as the current would have decreased to zero.

d] left plate is positive, right is negative

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