Textbook Question
Consider the circuit of Fig. E25.30. (b) What is the power output of the 16.0-V battery?
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Ch 25: Current, Resistance, and EMF
Chapter 25, Problem 25
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. (b) how much energy is transferred?
Verified step by step guidance1
Identify the given values: Current (I) = 12 A, Voltage (V) = 25 V, and Time (t) = 3.0 ms.
Convert the time from milliseconds to seconds for consistency in units. Recall that 1 ms = 0.001 seconds, so 3.0 ms = 0.003 seconds.
Use the formula for electrical power, which is P = V * I, where P is power, V is voltage, and I is current.
Calculate the power using the values of voltage and current.
Finally, use the formula for energy, which is E = P * t, where E is energy, P is power, and t is time. Substitute the power calculated in the previous step and the time in seconds to find the energy transferred.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Ohm's Law
Ohm's Law states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. This relationship is expressed as V = IR. Understanding this law is crucial for analyzing electrical circuits, including those involving medical devices like defibrillators.
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Resistance and Ohm's Law
Electrical Energy
Electrical energy is the energy derived from electric potential energy or kinetic energy. It can be calculated using the formula E = VQ, where E is energy, V is voltage, and Q is charge. In the context of the defibrillator, knowing how to calculate the energy transferred during the shock is essential for understanding its effectiveness in restarting the heart.
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Power and Energy Transfer
Power is the rate at which energy is transferred or converted and is calculated using the formula P = IV, where P is power, I is current, and V is voltage. The total energy transferred over a specific time can be found by multiplying power by time (E = Pt). This concept is vital for determining how much energy is delivered by the defibrillator during the brief application of current.
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Related Practice
Textbook Question
Consider the circuit of Fig. E25.30. (c) At what rate is electrical energy being converted to other forms in the 8.0-V battery?
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Textbook Question
Electric eels generate electric pulses along their skin that can be used to stun an enemy when they come into contact with it. Tests have shown that these pulses can be up to 500 V and produce currents of 80 mA (or even larger). A typical pulse lasts for 10 ms. What power and how much energy are delivered to the unfortunate enemy with a single pulse, assuming a steady current?
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Textbook Question
The battery for a certain cell phone is rated at 3.70 V. According to the manufacturer it can produce 3.15 * 10^4 J of electrical energy, enough for 5.25 h of operation, before needing to be recharged. Find the average current that this cell phone draws when turned on.
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Textbook Question
A typical small flashlight contains two batteries, each having an emf of 1.5 V, connected in series with a bulb having resistance 17 Ω. (a) If the internal resistance of the batteries is negligible, what power is delivered to the bulb?
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Textbook Question
A typical small flashlight contains two batteries, each having an emf of 1.5 V, connected in series with a bulb having resistance 17 Ω. ((b) If the batteries last for 5.0 h, what is the total energy delivered to the bulb?
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