CourseNotes.29 - 8.1 Work Energy and Emf An ‘emf...

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Unformatted text preview: 8.1 Work, Energy, and Emf An ‘emf device’ is a word from antiquity which we still use, but it means in essence, a device which produces a potential difference. Emf (given the symbol E ) stands for electromotive force which is a misnomer because as we will see shortly, emf is not a force but rather a potential difference. Emf is defined through the work which it does on charges E = dW dq (25) When talking about emf devices, we make a distinction between an ideal and a real emf device. An ideal emf device lacks any internal resistance. Hence, if we were to hook up an ideal emf device to a circuit without any resistance it would drive current through the wire infinitely fast. A real emf device has some internal resistance and hence, when hooked up to a circuit without any resistance will have a limit to how much current it can drive. Note that all emf devices are real devices. We can (and will) treat a real emf device as an ideal one hooked up in series with a resistor whose value is set by the internal resistance of the real emf device.resistor whose value is set by the internal resistance of the real emf device....
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