Flashlight battery

An electrochemical cell can be defined as two conductors or electrodes, usually metallic, immersed in the same electrolyte solution, or in two different electrolyte solutions which are in electrical contact. Electrochemical cells are classed into two groups. A galvanic (sometimes, voltaic) cell is one in which electrochemical reactions occur spontaneously when the two electrodes are connected by a conductor. These cells are often employed to convert chemical energy into electrical energy. Many types are of commercial Importance, such as the lead-acid battery, flashlight batteries, and various fuel cells. An electrolytic cell is one in which chemical reactions are... 

Jmjm any of the things we deal with in real life are related either directly or WWW indirectly to electrochemical reactions. Think of all the things around you that contain batteries — flashlights, watches, automobiles, calculators, PDAs, pacemakers, cell phones, toys, garage door openers, and so on. 

All flashlight batteries, button batteries, compact rechargeable batteries and vehicle storage batteries operate under the same basic principles. An electrochemical cell is constructed of two chemicals with different electron-attracting capabilities. Called an electrochemical couple, these two chemicals, itntncrscd in an electrolyte (material that carries the flow of energy between electrodes), are connected to each other through an external circuit. 

A battery stores electric energy. Although the concentration of energy is small compared, for example to gasoline, we see a myriad of uses of batteries in radios, cellular phones, flashlights, computers, watches, and so on. The public s demand for these portable products is ever increasing, and scientists strive to develop lighter and better batteries. 

Electrochemical cells are familiar—a flashlight operates on current drawn from electrochemical cells called dry cells, and automobiles are started with the aid of a battery, a set of electrochemical cells in tandem. The last time you changed the dry cells in a flashlight because the old ones were dead, did you wonder what had happened inside those cells Why does electric current flow from a new dry cell but not from one that has been used many hours We shall see that this is an important question in chemistry. By studying the chemical reactions that occur in an electrochemical cell we discover a basis for predicting whether equilibrium in a chemical reaction fa-... 

Electron-transfer reactions occur all around us. Objects made of iron become coated with mst when they are exposed to moist air. Animals obtain energy from the reaction of carbohydrates with oxygen to form carbon dioxide and water. Turning on a flashlight generates a current of electricity from a chemical reaction in the batteries. In an aluminum refinery, huge quantities of electricity drive the conversion of aluminum oxide into aluminum metal. These different chemical processes share one common feature Each is an oxidation-reduction reaction, commonly called a redox reaction, in which electrons are transferred from one chemical species to another. 

Redox reactions can proceed by direct transfer of electrons between chemical species. Examples include the rusting of iron and the metabolic breakdown of carbohydrates. Redox processes also can take place by indirect electron transfer from one chemical species to another via an electrical circuit. When a chemical reaction is coupled with electron flow through a circuit, the process is electrochemical. Flashlight batteries and aluminum smelters involve electrochemical processes. 

C19-0125. The first battery to find widespread commercial use was the carbon-zinc dry cell, in which the cathode reaction is 2 Mn02( ) + q)+2e -> ZnMn2 04( ) In a flashlight, one of these batteries... 

The Leclanche cell (also known as the dry cell) is frequently used to power flashlights, watches, calculators, and a number of other portable devices. Despite the name dry cell, this battery does contain an electrolyte solution but only in the form of dense paste. There are two versions of this cell, the acid version and the alkaline version. 

A lead-acid storage battery is only one type of battery, however. Different batteries use different metals and electrolytes to make them work. For example, alkaline batteries (the ones found in flashlights, toys, and portable electronic devices) contain powdered zinc and manganese dioxide as their electrodes. They use an electrolyte made of an alkaline solution of potassium hydroxide. Most alkaline batteries have a finite amount of chemicals in them. Once the chemicals react with one another, they are used up, and the battery goes dead (is discharged) and cannot be recharged. 

Test the device with a battery and flashlight bulb. Pressure on the top lid should push the sharp points through the paper to make contact with the lid below, thus completing a circuit. The amount of pressure required can be varied by using paper of different types or thickness. 

Check the operation of the device with a battery and flashlight bulb and determine the proper... 

Now test the circuit with battery and flashlight bulb. If the blade is held or secured midway between the two nails the circuit should be open. If the blade is moved to touch either of the nails, the circuit should close. 

Apply current with flashlight batteries to fire. To be safe, the operator should not be closer than 50 yards directly behind the rocket when it is fired. 

The main fields of application for this battery chemistry include portable TVs, radio receivers, lamps, flashlights, electric shavers, barrier lightning, instruments, batteries for portable rechargers, emergency power supplies, small refrigerators, power sources for tourists, hunters, geologists, shepherds and so on. Parameters of some batteries, assembled from the modules, are summarized in Table 4. 

Fuel cells are also inherently flexible. Like batteries in a flashlight, the cells can be stacked to produce voltage levels that match specific power needs from a few watts for certain appliances to multiple megawatt power stations that can light a community. 

Modern dry cells are closely modelled on the Leclanche cell, and also contain electrolyte pastes. You have probably used dry cells in all kinds of applications, such as lighting a flashlight, powering a remote control, or ringing a doorbell. Dry cells are inexpensive. The cheapest AAA-, AA-, C-, and D-size 1.5-V batteries are dry cells. 

O If two 1.5-V D-size batteries power a flashlight, at what voltage is the flashlight operating Explain. 

A D-size dry cell flashlight battery is much bigger than a AAA-size dry cell calculator battery. However, both have cell potentials of 1.5 V. Do they supply the same quantity of electricity Explain your answer. 

Meanwhile, scientists studied the electrical activity of neurons. They discovered that the messages neurons pass to one another consist of brief electrical impulses known as action potentials. Neurons (and most other cells) have a small electrical potential of about 60 millivolts between their interior and exterior—this voltage, which is only about 4 percent as strong as a typical flashlight battery, exists across the cell s membrane. 

Batteries are needed to power small, portable instruments such as flashlights, cameras, and computers. In many flashlight batteries, the two electrodes—attached to the plus and minus ends of the battery—... 

Once a hypothesis is formulated, an experiment is conducted to test the hypothesis. Experimentation is what distinguishes chemistry, and other experimental science, from other disciplines. In simple experiments, the researcher designs the experiment to examine one independent variable and attempts to hold all other variables constant. Again, using the battery example, if the experiment was designed to test battery life in flashlights, then battery life would be the dependent variable. It would be im-portant to define in exact terms the variable battery life and exactly how it would be measured. The researcher would then attempt to control all other variables, except for one indepen-... 

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