How much power is produced if a voltage of $3 V$ $3 V$ is applied to a circuit with a resistance of $21 Omega$ ?

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Answer 1 · 2016-02-29T05:40:56

$3/7 W$ or $428.571 mW$

Let P be power dissipated from 21 ohm resistor to ambient.

Let V be the voltage applied across 21 ohm resistor.

Let I be the current passing through 21 ohm resistor.

We know that power defined as the product of voltage across resistor and current through resistor

Therefore, $P=VI$ $------(1)$

By ohm's law, $V=IR$

$=>I=V/R$ $------(2)$

from (1) and (2)

$P=V xx V/R$

$P=V^2/R$

substitute V=3 volts and R=21 ohms

$=> P=3^2/21$

$=>P=9/21$

$=>P=3/7$ watts

$=>P=0.428571$ watts

$=>P=428.571 mW$

How much power is produced if a voltage of 3 V3V3 V is applied to a circuit with a resistance of 21 Omega21 Omega?