Defibrillator Advice.com

During a heart attack, the upper and
lower parts of the heart can begin
contracting at different rates. Often
these contractions are extremely
rapid. This fluttery unsynchronized
beating, called fibrillation, pumps
little or no blood and can damage
the heart. A defibrillator uses a jolt
of electricity to momentarily stop
the heart so that it can return to a
normal beat
A defibrillator consists of two
parallel charged plates called a parallel-plate
capacitor, connected to a power
supply and discharging pads. A typical
defibrillator stores about 0.4 C
on the plates, creating a potential
difference of approximately 2 kV
between the plates.
When discharged through conductive
pads placed on the patient’s
chest, the capacitor delivers about
0.4 kJ of electrical energy in 0.002 s.
Roughly 200 J of this energy passes
through the patient’s chest.
A defibrillator uses a highvoltage
capacitor to help save lives.
Such capacitors have many other
applications in other electrical and
electronic devices, such as the highvoltage
power supplies for cathoderay
tubes in older televisions and
computer monitors.
The charge stored in such capacitors
can be dangerous. Products containing
such high-voltage capacitors
are designed to protect the users from
any dangerous voltages. However,
service technicians must be careful
when working on these devices.
Since the capacitors store charge,
they can deliver a nasty shock even
after the device is unplugged.
Questions
1. How does the magnitude of the
power delivered by the plates
compare with the actual power
delivered to the chest by the jolt?
2. Identify a feature of televisions
that demonstrates an important
application of parallel-plate
capacitors.
3. If a defibrillator can store 0.392 C
of charge in 30 s, how many
electrons are stored in this
time period?

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