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Question 26.57: An 18.0 W device has 9.00 V across it. How much charge goes ......

An 18.0 W device has 9.00 V across it. How much charge goes through the device in 4.00 h?

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We find the current from Eq. 26-26: i = P/V = 2.00 A. Then, from Eq. 26-1 (with constant current), we obtain

P=i V \quad \text { (rate of electrical energy transfer). }           (26-26)

i=\frac{d q}{d t} \qquad \text { (definition of current). }        (26-1)

\Delta q=i \Delta t=2.88 \times 10^4 \,C

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