Unformatted text preview: late the product of the terminal voltage and curent. For the refeience sys-tems shoM in Fis.2.6. we x'dte \2.6) wheno = iRand (2.7) when 1' = -iR. A second method of expressing the power at the terminals ol a resis-tor expresses power in terms of the currcnt arld the resistance. Substitutirg Eq. 2.1 into Eq. 2.6,we obtain Power in a resistor in terms of current b' P = i 2 R Likewise, substituting Eq.2.2 into Eq.2.7,we have p = -1)i : -(-i R)i = i2R. (2.e) p = u i = ( i R ) i p (2.8) Equations 2.8 and 2.9 are identical and demonstrate clearly that, regard_ less of voltage polarity and current direction, the powel at the terminals of a resistor is positive. Therefore, a resistor absorbs power from the circuit. A tlird method of expressing the power at the teminals of a iesistor is in terms of the voltage and resistance The expression is independent of the Dolaritv references. so R Power in a resistor in tenns of vottage F (2.10)...
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- Spring '07
- Resistor, Electrical resistance, Electrical impedance, Series and parallel circuits, ideal resistors