Chapter 27: Q. 15 (page 762)
15. A hollow copper wire with an inner diameter of and an outer diameter of carries a current of . What is the current density in the wire?
Short Answer
The current density in the wire is .
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Chapter 27: Q. 15 (page 762)
15. A hollow copper wire with an inner diameter of and an outer diameter of carries a current of . What is the current density in the wire?
The current density in the wire is .
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The conducting path between the right hand and the left hand can be modeled as a 10-cm-diameter, 160-cm-long cylinder. The average resistivity of the interior of the human body is 5.0 Ω m. Dry skin has a much higher resistivity, but skin resistance can be made negligible by soaking the hands in salt water. If skin resistance is neglected, what potential difference between the hands is needed for a lethal shock of 100 mA across the chest? Your result shows that even small potential differences can produce dangerous currents when the skin is wet.
II You need to design a fuse that "blows" if the current exceeds . The fuse material in your stockroom melts at a current density of . What diameter wire of this material will do the job?
The electron drift speed in a wire is exceedingly slow-typically only a fraction of a millimeter per second. Yet when you turn on a flashlight switch, the light comes on almost instantly. Resolve this apparent paradox.
16. A car battery is rated at , meaning that it can supply a current for before being completely discharged. If you leave your headlights on until the battery is completely dead, how much charge leaves the battery?
The current in a lightbulb is . The filament inside the bulb is in diameter.
a. What is the current density in the filament?
b. What is the electron current in the filament?
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