Problem: A circuit results from a source that creates a constant .01000 Volt potential difference across a resistance of 5 Ohms. What is the current through the resistor and how much power is delivered by the source?
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Solution: A source of .01000 Volts over a resistance of 2 Ohms will result in a current of ( .01000 V)/( 2 ohm) = .005 Amps = .005 C/s. Since .005 C is associated with ( .005 C)( .01000 Volts) = ( .005 C)( .01000 J/C) = .00005 J of work, .005 C/s will result in .00005 J/s = .00005 watts.
Generalized Response:
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Figure description: The figure below charts the relationships among voltage, resistance, current and power. The 'blue' triangle shows how voltage, current and resistance are related. (Greater voltage or less resistance implies greater current, reflecting I = V / R; resistance is the ratio of voltage to current, reflecting R = V / I; a current I through a resistance R requires a greater voltage drop pfor a greater current and for a greater resistance, reflecting V = I * R).
The 'green' triangle shows how power is the product of current and voltage (current is measured in C / s, voltage in J / C, so the product of current and voltage is the number of J / s, or watts, of power).
The relationship P = I * V can be combined with either I = V / R or with V = I * R to yield either P = I * (I * R) = I^2 * R or P = (V / R ) * V = V^2 / R.
