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P 2.5-1 A current
source and a voltage source are connected in
parallel with a resistor as shown in Figure P 2.5-1. All of the elements
connected in parallel have the same voltage, vs in this circuit. Suppose that vs = 15 V, is
= 3 A, and R = 5 Ω. (a)
Calculate the current i
in the resistor and the power absorbed by the resistor. (b) Change the
current source current to is
= 5 A and recalculate the current, i, in the
resistor and the power absorbed by the resistor. |
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Answer: i = 3 A and the resistor absorbs 45 W both when is = 3 A and when is = 5 A. |
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Figure
P 2.5-1 |
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(a) Calculate the current i in the
resistor and the power absorbed by the resistor. |
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Current in R is found from Ohm’s
law |
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Power can be found from |
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(b) Change the current source current to is = 5 A and recalculate the current, i, in the resistor and the power
absorbed by the resistor. |
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Since neither
vs or R change, the current in R cannot change. If the current in R does not change then
the power absorbed does not change. Moreover since the voltage across R does not change power
also cannot change. |
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