Chapter 22, Problem 3STP

To determine

To choose: The correct option.

Answer to Problem 3STP

The correct option is (C), 2.3 W.

Explanation of Solution

Given:

A flashlight with a current of 0.5 A flowing through it and the voltage is the sum of the voltages of the individual batteries, each of voltage 1.5 V.

Formula used:

The power delivered to the bulb of the flashlight is a function of current flowing through it, I and voltage drop across it, V ,which can be expressed as,

  $P=VI$

Calculation:

In the given flashlight shown in Figure 1, the cells are arranged in series such that, the voltages add up.

  

Thus, the total voltage of the flashlight is,

  $\begin{array}{c}V=1.5\times 3\\ =4.5\text{ V}\end{array}$

Substituting the voltage and current value, the power can be obtained as,

  $\begin{array}{c}P=4.5\times 0.5\\ =2.25\text{}\text{ W}\\ \simeq \text{2}\text{.3 W}\end{array}$

Conclusion:

Therefore, the correct option representing the power delivered to the bulb in the flashlight is (C), 2.3 W.