Question

Most flashlights use two or more batteries in series. Use the concepts of galvanic cells in this chapter to explain why a flashlight with two new batteries and one "dead" battery will give only a dim light if any light is obtained at all.

Short answer

A flashlight with two new batteries and one 'dead' battery provides only dim light because the 'dead' battery lowers the total voltage and can introduce high internal resistance, leading to less current flow through the bulb.

Step-by-step solution

Understanding Batteries in Series

When batteries are connected in series, the total voltage supplied is the sum of the individual voltages of each battery. If one battery is 'dead,' its voltage contribution is significantly less than that of a new battery.

Role of a 'Dead' Battery in the Circuit

A 'dead' battery has used up most of the chemical energy that can be converted into electrical energy. Therefore, it cannot provide the same voltage as a new battery and may also introduce high internal resistance.

Effect on the Flashlight Performance

Because the total voltage is reduced due to the 'dead' battery, the current through the flashlight bulb is lower. This lower current results in a dimmer light because the filament in the bulb doesn't get as hot, producing less light.

Galvanic Cells Concept Application

In a galvanic cell, the chemical reaction must occur for electricity to flow. If one of the cells (the 'dead' battery) cannot sustain the reaction, it reduces the overall efficiency and output of the battery chain.

Key concepts

Battery Voltage In Series

In the realm of electronics, understanding how battery voltage operates when batteries are arranged in series is a key concept. Imagine lining up several batteries end-to-end like train cars. The positive end of one battery connects to the negative end of the next, establishing a series circuit. The total voltage output in this lineup is the sum of each battery's voltage. For example, if you have three 1.5-volt batteries in series, the total voltage provided to power a device, such as a flashlight, would be 4.5 volts.

However, the efficiency of this configuration hinges on the condition of each battery. If all batteries are new, the voltage of each cell adds up neatly, powering your device effectively. The problem occurs when we intermix a 'dead' battery; this faulty cell has minimal voltage and can't contribute its share to the total, resulting in a lower overall voltage. This directly affects devices dependent on a specific voltage level for optimal operation.

Effect of Dead Battery on Circuit

A 'dead' battery doesn't simply vanish from the circuit when it can no longer contribute power. Instead, it becomes an obstacle. Internally, a spent battery builds up resistance, which hinders the flow of electrical current. This internal resistance is analogous to having a clogged pipe in a water system—it impedes flow.

When one battery in a series is 'dead', not only does it fail to contribute power, but it also introduces a sort of electrical 'friction'. Therefore, it's not just about the lack of voltage; the dead battery actively works against the current, pulling down the circuit's overall performance. Devices that require a certain level of power to operate correctly, like a flashlight, will exhibit noticeably poorer functionality—this could be dim light or inability to turn on, signaling it's time to replace the problematic battery.

Current Reduction and Light Intensity

The intensity of light emitted from a bulb is a direct consequence of the electric current flowing through it. In essence, the filament inside the bulb must heat to a high temperature for a bright light, which requires a substantial current. This leads to a simple rule: the brighter you want the light, the more current you need.

Under the unwelcome scenario of a dead battery in a series, the total current mustered by the cells is reduced. The diminished current can't heat the filament as much, resulting in a drop in light intensity—your flashlight shines dimly. The correlation between current and brightness is a fundamental principle of electric lighting, making the proper maintenance of power sources, like batteries, all the more crucial for consistent performance.