May 2005
Beginner to intermediate
398 pages
12h 12m
English
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Power
A voltage difference is generated by a difference in potential energy between two points. Therefore, to generate a voltage, you use a device that can create such an energy difference. Such devices may be mechanical (generators), converting motion into a potential difference by electromagnetics; photovoltaic (solar cells); or chemical (batteries). Conversely, a voltage difference (and therefore current flow) can be used to produce mechanical movement (motors), light emission (light bulbs, LEDs), and heat (toasters, Pentium 4 processors).
Power is the amount of work per time (Joules per second) and is measured in Watts (unit symbol "W"). The equation for calculating power is simply:
P = V * I
No electronic device is 100% efficient (far from it!), and so it will consume power as it performs its task. The power consumed by a device may be calculated using the above equation, from the voltage difference across the device and the current flowing through the device. A typical embedded computer may consume a few hundred mW (milliWatts) of power, but it can vary quite considerably. A large and powerful embedded machine may use several tens (or even hundreds) of Watts, while a tiny embedded controller may use just microWatts.
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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