Question

A lamp is mapped 12v,24w.how many joules does it consume in an hour and what is the current it passes?

Answer 1

Explanations & Calculations

• The description on the lamp says that the lamp consumes/performs at a power of 24Watts when it is provided with 12V.
• Therefore, to do the needed calculations, assume the lamp is performing at full power: 24W

• Watts (W) is Joules per second (J/s), therefore, energy consumed over a period of one hour is

$\qquad\qquad \begin{aligned} \small E&= \small power \times time\\ &= \small 24W\times 1\times 3600s\\ &= \small \bold{86400J} \end{aligned}$

• If the current pass through the lamp is $\small i$, then using the relationship $\small Power=Vi$

$\qquad\qquad \begin{aligned} \small i&= \small \frac{24W}{12V}\\ &= \small \bold{2A} \end{aligned}$