Context: A galvanic cell, or voltaic cell, named after Luigi Galvani, or Alessandro Volta respectively, is an electrochemical cell that derives electrical energy from spontaneous redox reactions taking place within the cell. It generally consists of two different metals connected by a salt bridge, or individual half-cells separated by a porous membrane., An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or facilitating chemical reactions through the introduction of electrical energy. A common example of an electrochemical cell is a standard 1.5-volt cell meant for consumer use. This type of device is known as a single Galvanic cell. A "battery" consists of two or more cells, connected in either parallel or series pattern., An electric battery is a device consisting of two or more electrochemical cells that convert stored chemical energy into electrical energy . Each cell has a positive terminal , or cathode , and a negative terminal , or anode . The terminal marked positive is at a higher electrical potential energy than is the terminal marked negative . The terminal marked negative is the source of electrons that when connected to an external circuit will flow and deliver energy to an external device . When a battery is connected to an external circuit , electrolytes are able to move as ions within , allowing the chemical reactions to be completed at the separate terminals and so deliver energy to the external circuit . It is the movement of those ions within the battery which allows current to flow out of the battery to perform work . Although the term battery technically means a device with multiple cells , single cells are also popularly called batteries . Primary ( single - use or `` disposable '' ) batteries are used once and discarded ; the electrode materials are irreversibly changed during discharge . Common examples are the alkaline battery used for flashlights and a multitude of portable devices . Secondary ( rechargeable batteries ) can be discharged and recharged multiple times ; the original composition of the electrodes can be restored by reverse current . Examples include the lead - acid batteries used in vehicles and lithium - ion batteries used for portable electronics . Batteries come in many shapes and sizes , from miniature cells used to power hearing aids and wristwatches to battery banks the size of rooms that provide standby power for telephone exchanges and computer data centers . According to a 2005 estimate , the worldwide battery industry generates US $ 48 billion in sales each year , with 6 % annual growth . Batteries have much lower specific energy ( energy per unit mass ) than common fuels such as gasoline . This is somewhat offset by the higher efficiency of electric motors in producing mechanical work , compared to combustion engines ., A cathode is the electrode from which a conventional current leaves a polarized electrical device. (This definition can be recalled by using the mnemonic "CCD" for "cathode current departs".) A conventional current describes the direction in which positive electronic charges move. Electrons have a negative charge, so the movement of electrons is opposite to the conventional current flow. Consequently, the mnemonic "cathode current departs" also means that electrons flow into the device's cathode., The electron is a subatomic particle, symbol or , with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the electron include an intrinsic angular momentum (spin) of a half-integer value, expressed in units of the reduced Planck constant, "". As it is a fermion, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle. Like all matter, electrons have properties of both particles and waves: they can collide with other particles and can be diffracted like light. The wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a larger De Broglie wavelength for a given energy., An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). The word was coined by William Whewell at the request of the scientist Michael Faraday from the Greek words "elektron", meaning amber (from which the word electricity is derived), and "hodos", a way., Subject: battery , Relation: source_of_energy, Options: (A) electricity (B) light (C) redox
Output: redox