Glossary

Batteries are the unsung heroes of our electronic world. They provide the juice that powers our devices, from smartphones to cars. Understanding how they work and their key characteristics is crucial for grasping the basics of electrical circuits.

and are key concepts in function. Chemical reactions inside batteries generate electrical energy, with different types of batteries using various materials. Calculating helps us understand how batteries perform under load.

Electromotive Force and Batteries

Emf and battery potential difference

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  • (emf) represents the maximum potential difference between terminals when no flows
    • Measured in volts (V)
    • Indicates the battery's capacity to drive current through a
  • Potential difference is the drop across the battery when current flows
    • Always less than the emf due to of the battery
  • Relationship between emf (E\mathcal{E}) and potential difference (ΔV\Delta V) given by ΔV=E−Ir\Delta V = \mathcal{E} - Ir
    • II represents the current flowing through the battery
    • rr is the of the battery
  • The emf creates an electric field within the battery, driving the flow of charge

Chemical reactions in battery voltage

  • Batteries generate electrical energy from chemical energy via redox reactions ()
  • Primary batteries are non-rechargeable and include:
    • Alkaline batteries (AA, AAA) with zinc () and manganese dioxide ()
      • Zn oxidizes, releasing electrons while MnO2 reduces, accepting electrons
    • Lithium batteries (CR2032) with lithium () anode and various cathode materials (manganese dioxide, carbon monofluoride)
      • Li oxidizes, releasing electrons and cathode material reduces, accepting electrons
  • Secondary batteries are rechargeable and include:
    • Lead-acid batteries (car batteries) with lead () anode, lead dioxide () cathode, and sulfuric acid () electrolyte
      • During discharge, Pb and PbO2 react with H2SO4 to form lead sulfate ()
      • During charging, PbSO4 converts back to Pb and PbO2
    • Lithium-ion batteries (smartphone batteries) with graphite anode and lithium metal oxide cathode (, )
      • During discharge, Li ions move from anode to cathode while electrons flow through the external circuit
      • During charging, Li ions move back to the anode

Calculation of battery terminal voltage

  • (VTV_T) is the potential difference across battery terminals when current flows
  • Relationship between terminal voltage, emf (E\mathcal{E}), current (II), and internal (rr) given by VT=E−IrV_T = \mathcal{E} - Ir
  • To calculate terminal voltage:
    1. Identify the emf (E\mathcal{E}) and internal resistance (rr) of the battery
    2. Determine the current (II) flowing through the battery
    3. Substitute values into the equation VT=E−IrV_T = \mathcal{E} - Ir
  • Example: A 12 V battery has an internal resistance of 0.1 Ω and supplies a current of 5 A
    • Given: E=12\mathcal{E} = 12 V, r=0.1r = 0.1 Ω, I=5I = 5 A
    • Calculation: VT=E−Ir=12V_T = \mathcal{E} - Ir = 12 V −(5- (5 A)(0.1)(0.1 Ω)=11.5) = 11.5 V
    • The terminal voltage of the battery is 11.5 V when supplying a current of 5 A

Electrochemistry and Battery Function

  • is the study of chemical reactions that produce electrical energy
  • Batteries convert chemical into electrical potential energy
  • In a circuit, the battery's emf drives from the negative terminal to the positive terminal
  • The electrochemical reactions in batteries involve the transfer of electrons between chemical species, creating a potential difference

Key Terms to Review (40)

Ac current: AC current, or alternating current, is an electric current that reverses direction periodically. It is commonly used in power supply systems due to its efficient transmission over long distances.
Ac voltage: AC voltage is a type of electrical current where the voltage periodically changes direction. It is commonly used in household power supplies and electrical grids due to its efficiency in long-distance transmission.
Ampere: An ampere (A) is the unit of electric current in the International System of Units (SI). It is defined as the flow of one coulomb of charge per second.
Ampere: The ampere (symbol: A) is the base unit of electric current in the International System of Units (SI). It is defined as the constant flow of one coulomb of electric charge per second, and it is a fundamental quantity in the study of electromagnetism and electrical circuits.
Anode: An anode is the electrode where oxidation occurs and electrons are given off in a direct-current circuit. It is typically considered the positive terminal in a device like a battery.
Back emf: Back electromotive force (back emf) is the voltage generated by an electric motor or generator that opposes the applied voltage. It is a consequence of electromagnetic induction and acts to limit the current in the circuit.
Battery: A battery is a device that converts chemical energy into electrical energy to provide a steady flow of direct current (DC). It consists of one or more electrochemical cells with external connections for powering electrical devices.
Battery: A battery is a device that stores chemical energy and converts it into electrical energy. It is a primary source of electrical power that can be used to power various electronic devices and circuits.
Battery testers: Battery testers are devices used to measure the state of charge, voltage, and overall health of a battery. They help determine whether a battery can still effectively provide electromotive force (EMF) in circuits.
Cathode: The cathode is the electrode where reduction occurs in an electrochemical cell, drawing positive ions from the electrolyte. It serves as the source of electrons in a direct-current circuit.
Circuit: A circuit is a closed loop through which an electric current flows. It consists of various electrical components, such as power sources, switches, and loads, connected by conductive paths that allow the flow of electric charge.
Current: Current is the rate of flow of electric charge through a given area, typically measured in amperes (A). It is a fundamental concept in the study of electricity and electromagnetism, as it describes the movement of electric charges and is essential for understanding various electrical phenomena.
Electrochemistry: Electrochemistry is the branch of chemistry that deals with the relationship between electrical energy and chemical reactions. It encompasses processes where electrons are transferred, leading to chemical changes, which are fundamental in batteries, fuel cells, and electrolysis. Understanding electrochemistry is crucial for various applications, including energy storage and conversion technologies.
Electromotive Force: Electromotive force (EMF) is the voltage or potential difference generated in an electrical circuit, typically by a source of electrical energy such as a battery or generator. It is the driving force that causes electric charge to flow through a circuit, enabling the conversion of other forms of energy into electrical energy.
Electromotive Force (EMF): Electromotive force, or EMF, is the voltage or potential difference generated by a source of electrical energy, such as a battery, generator, or other electrochemical device. It represents the maximum possible voltage that can be delivered by the source, and it drives the flow of electric current through a circuit.
Electron Flow: Electron flow refers to the movement of electrons through a conductive material, such as a metal wire or semiconductor, driven by an electromotive force (EMF). This flow of electrons is the fundamental basis for the generation and transmission of electrical current, which is essential in understanding both electrical current and electromotive force.
Equivalent resistance: Equivalent resistance is the total resistance of a combination of resistors connected either in series or parallel. It simplifies complex circuits into a single resistor value that has the same effect on the circuit.
H2SO4: H2SO4, or sulfuric acid, is a highly corrosive and versatile chemical compound that plays a crucial role in various industrial and scientific applications, including the context of electromotive force (EMF).
Internal resistance: Internal resistance is the resistance within a battery or any other voltage source that causes a loss in the output voltage as current flows through it. It is an intrinsic property of the source, often affecting the overall efficiency of electrical circuits.
Internal Resistance: Internal resistance is an inherent property of an electrical source, such as a battery or generator, that opposes the flow of electric current through the source itself. It arises from the resistance of the internal components and materials within the source and can have a significant impact on the performance and behavior of electrical circuits.
Lead acid battery: A lead-acid battery is a type of rechargeable battery that uses lead dioxide and sponge lead as electrodes, and sulfuric acid as the electrolyte. Commonly used in automotive applications, it converts chemical energy to electrical energy through redox reactions.
Li: Li, or lithium, is a soft, silver-white metallic element that is the lightest of all metals. It is a key component in the study of electromotive force, as it plays a crucial role in electrochemical processes and the generation of electrical energy.
LiCoO2: LiCoO2, or lithium cobalt oxide, is a compound commonly used as a cathode material in lithium-ion batteries. It is known for its high energy density and stable electrochemical performance, making it a popular choice for powering portable electronics and electric vehicles. Its structure facilitates the intercalation of lithium ions, which is essential for the battery's operation.
LiFePO4: LiFePO4, or lithium iron phosphate, is a type of lithium-ion battery chemistry that is widely used in various applications due to its safety, stability, and long cycle life. It is a cathode material that provides a stable and efficient source of energy storage.
MnO2: MnO2, or manganese dioxide, is an inorganic compound composed of one manganese atom and two oxygen atoms. It is a dark-colored, crystalline solid that is commonly used in various applications, including as a cathode material in batteries, a pigment in glass and ceramics, and a reagent in chemical reactions.
Oxidation-Reduction Reactions: Oxidation-reduction (redox) reactions are a fundamental class of chemical reactions where the oxidation state of atoms is changed. In these reactions, one substance loses electrons (gets oxidized) while another substance gains electrons (gets reduced), resulting in the transfer of electrons between the reactants.
Pb: Pb is the chemical symbol for lead, a heavy metal that is denser than most common materials. In the context of electromotive force, it is significant because lead-acid batteries utilize lead dioxide (PbO2) and sponge lead (Pb) as electrodes, making it crucial for understanding energy storage and conversion processes in electrochemical cells.
PbO2: PbO2, or lead(IV) oxide, is a chemical compound consisting of lead and oxygen, commonly used in various applications including batteries and electrochemistry. In the context of electromotive force, PbO2 plays a critical role as the active material in lead-acid batteries, influencing both the voltage produced and the overall efficiency of the electrochemical reactions that take place during battery operation.
PbSO4: PbSO4, or lead sulfate, is an inorganic compound formed from lead and sulfuric acid. It plays a crucial role in lead-acid batteries, where it acts as a reactant during the charging and discharging processes, directly linking it to the concept of electromotive force through its involvement in electrochemical reactions.
Potential difference: Potential difference, also known as voltage, is the work needed to move a charge from one point to another in an electric field. It is measured in volts (V).
Potential drop: Potential drop is the decrease in electric potential energy per unit charge as a current flows through a component or resistor in a circuit. It is measured in volts (V).
Potential Energy: Potential energy is the stored energy in an object due to its position or configuration in a force field, such as gravitational or electric fields. This form of energy can be converted into kinetic energy when the object is allowed to move or change position, playing a crucial role in various physical systems. Understanding potential energy helps explain how electric forces act between charges and the concept of voltage in electric circuits.
Resistance: Resistance is a measure of the opposition to the flow of electric current in an electrical circuit. It is a fundamental concept in understanding the behavior of electric circuits and the relationship between voltage, current, and power.
Terminal voltage: Terminal voltage is the potential difference measured across the terminals of a battery or power supply when a current is flowing. It differs from the electromotive force (emf) due to the internal resistance of the power source.
Terminal Voltage: Terminal voltage, also known as terminal potential difference, refers to the voltage or potential difference measured across the terminals of an electrical device or component, such as a battery, generator, or resistor. It represents the available voltage at the output of the device, which can be used to power other electrical circuits or components.
Volt: The volt is the unit of electric potential and electromotive force in the International System of Units (SI). It represents the potential difference across a conductor when a current of one ampere dissipates one watt of power. The volt is a fundamental unit that is essential in understanding and quantifying various electrical phenomena, from the storage of energy in capacitors to the generation of alternating current in household wiring.
Voltage: Voltage, also known as electrical potential difference, is the driving force that causes the flow of electric current in a circuit. It is the measure of the potential energy difference between two points in an electrical system, and it is the key factor that determines the rate at which electric charge moves through a conductor.
Voltaic pile: A voltaic pile is the first electrical battery that could continuously provide an electric current to a circuit. It was invented by Alessandro Volta in 1800 and consists of alternating discs of zinc and copper separated by pieces of cardboard soaked in salt water.
Zn: Zn, or zinc, is a metallic chemical element that plays a crucial role in various electrochemical processes, particularly in the context of electromotive force. As an essential trace mineral, zinc is involved in numerous biological functions and is vital for human health and development.
ε: Epsilon (ε) is a mathematical symbol commonly used to represent a small, positive quantity or a variable that approaches zero. In the context of electromotive force, epsilon (ε) is often used to denote the electromotive force (EMF) or voltage generated by a source, such as a battery or a generator.
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