Chapter 18, Problem 2Q

When a flashlight is operated, what is being used up: battery current, battery voltage, battery energy, battery power, or battery resistance? Explain.

To determine

To explain:

The one from among current, voltage, energy, power or resistance of the battery that is being used when the flashlight works

Answer to Problem 2Q

Solution:

It is the battery’s energy which is used, when a flashlight operates. But on continuous use of the battery; its energy decreases, which in turn reduces the current, voltage and the power provided by it.

Explanation of Solution

A battery is first charged before being used by a flashlight or any other electrical equipment. The charging of a battery means more and more negatively charged electrons are accumulated at one terminal and an equal scarcity of electrons is maintained at other terminal. It may be performed by some chemical reaction or by allowing a reverse current to enter in the battery, i.e. from an external circuit; electrons enter into the battery through a negative terminal. In this way, the negative terminal acquires more and more electrons, i.e. battery becomes charged to be used for any job like to operate a flashlight.

But in this whole process of charging the battery, an external agent needs to perform the work to push more and more negatively charged electrons towards the negative terminal of the battery and this work is stored in the battery in form of its energy.

Now, when the battery is connected to external equipments like a flashlight, the stored energy is dissipated across the resistance of the bulb-filament, which appears in the form of light to us. But on continuous use of this energy, the potential difference between the two terminals keep on decreasing which in turn decreases the current and voltage provided by it to the flashlight.