A charge of $8 C$ $8 C$ passes through a circuit every $2 s$ $2 s$ . If the circuit can generate $3 W$ $3 W$ of power, what is the circuit's resistance?

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Answer 1 · 2016-12-19T13:40:20

I found: $0.2Omega$

You know that current $I$ is the rate of passing of charge $Q$ through a section of a conductor with time $t$ or:

$I=Q/t$

in your case:
$I=8/2=4A$

Power $P$ is the rate of transformation of energy with time that, in case of electrical circuits, can be written (using also Ohm's Law: $V=RI$ ):

$P=VI=V^2/R=I^2R$

using the last one:

$P=I^2R$ and rearranging:

$R=P/I^2=3/4^2=3/16=0.1875~~0.2Omega$

A charge of 8 C8C8 C passes through a circuit every 2 s2s2 s. If the circuit can generate 3 W3W3 W of power, what is the circuit's resistance?