Chapter 4.3, Problem 32R

To determine

To calculate: The electrical energy converted in one hour by a $5\text{ W}$ lightbulb.

Answer to Problem 32R

The electrical energy converted by the lightbulb is $\underset{\_}{\text{18,000 J}}$ .

Explanation of Solution

Given data:

Power of the lightbulb, $P=5\text{ W}$

Time, $t=1\text{ hour}$

Formula used:

Power Equation:

  $P=\frac{E}{t}$

Where $P$ is the power in watts, $E$ is the energy of the object in joules and $t$ is the time in seconds in which energy is converted.

Calculation:

As per the problem,

  $\begin{array}{l}P=5\text{W}\\ t=1\text{ hour= (1 hour)(60 min)(60 s)=3600s [1 hour= 60 min and 1 min=60 s]}\end{array}$

Substitute the values of power and time in the rearranged power equation to get energy:

  $\begin{array}{l}P=\frac{E}{t}\\ E=Pt\\ E=(5\text{ W)(3600 s)}\\ E=18,000\text{ J}\end{array}$

Conclusion:

The electrical energy converted by the lightbulb is $\underset{\_}{\text{18,000 J}}$ .