Chapter 12.3, Problem 22R

To determine

Emitted thermal energy.

Answer to Problem 22R

The required answer is $54J$ .

Explanation of Solution

Given:

Percentage of thermal energy emitted by an incandescent light bulb is $90\%$

Power of bulb is $60W$ .

Formula used:

Formula to calculate energy is

  $\text{E}=\text{Power }\times \text{ Time}$

Formula to calculate percentage is

  $\frac{Part}{Whole}\times 100=\%$

Calculation:

Power taken by bulb is $60W$ per second. So, energy will be

  $\begin{array}{l}\text{E}=\text{Power }\times \text{ Time}\\ \text{E}=60\text{W}\times 1\sec \\ \text{E}=60\text{J}\end{array}$

By using the formula of percentage, amount of thermal energy emitted is

  $\begin{array}{c}E=\frac{90}{100}\times 60J\\ =\frac{90}{10}\times 6J\\ =9\times 6J\\ =54J\end{array}$

Conclusion:

The emitted thermal energy is $54J$ .