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Ch 25: Current, Resistance, and EMF
Young & Freedman Calc - University Physics 14th Edition
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoYoung & Freedman Calc 14th EditionCh 25: Current, Resistance, and EMFProblema 41b
Capitolo 25, Problema 41b

A heart defibrillator is used to enable the heart to start beating if it has stopped. This is done by passing a large current of 12 A through the body at 25 V for a very short time, usually about 3.0 ms. How much energy is transferred?

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To find the energy transferred, we need to use the formula for electrical energy: \( E = V \times I \times t \), where \( E \) is the energy in joules, \( V \) is the voltage in volts, \( I \) is the current in amperes, and \( t \) is the time in seconds.
First, ensure all units are consistent. The time given is 3.0 ms, which needs to be converted to seconds. Since 1 ms = 0.001 seconds, 3.0 ms = 0.003 seconds.
Substitute the given values into the formula: \( V = 25 \) volts, \( I = 12 \) amperes, and \( t = 0.003 \) seconds.
Calculate the product \( V \times I \times t \) to find the energy transferred.
The result will give you the energy transferred in joules, which is the amount of energy delivered by the defibrillator during the 3.0 ms pulse.

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Electric Current

Electric current is the flow of electric charge through a conductor, measured in amperes (A). In the context of a defibrillator, a large current of 12 A is used to stimulate the heart muscle, helping it to resume its normal rhythm. Understanding current is crucial for calculating the energy transferred during the defibrillation process.
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05:38
Intro to Current

Voltage

Voltage, measured in volts (V), is the potential difference that drives the flow of electric current through a circuit. In a defibrillator, a voltage of 25 V is applied to the body to create the necessary conditions for current flow. Voltage is essential for determining the power and energy involved in the defibrillation process.
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RMS Current and Voltage

Energy Transfer

Energy transfer in electrical systems is calculated using the formula: Energy = Power × Time, where Power = Voltage × Current. For the defibrillator, the energy transferred can be found by multiplying the power (25 V × 12 A) by the duration of the current flow (3.0 ms). This concept is key to understanding how much energy is delivered to the heart during defibrillation.
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Overview of Heat Transfer
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