9.1 Electrical Current
2 min read•june 24, 2024
is the flow of electric charge through a conductor, driven by a difference in . It's measured in amperes, with one defined as the flow of one of charge per second.
flows from positive to negative, opposite to . Understanding current is crucial for analyzing circuits and electrical systems, forming the foundation for more complex concepts in electromagnetism.
Electrical Current
Definition of electrical current
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- Flow of electric charge through a conductor
- ( or ) move through the conductor
- (metals) allow charge to flow easily
- Current flows from higher () to lower electric potential
- In a , current flows from positive terminal to negative terminal
- direction defined as flow of positive charge
- In reality, electrons (negative charge) flow opposite to conventional current
Unit of electrical current
- (A) is the unit of
- One ampere defined as flow of one (C) of charge per second
- Relationship between current (), charge (), and time () given by:
- 10 coulombs of charge passing through a point in a in 5 seconds results in a current of 2 amperes
Conventional current vs electron flow
- Conventional current defined as flow of positive charge
- Historical convention still widely used in circuit analysis
- In a -powered circuit, conventional current flows from positive to negative terminal
- Electron flow is actual movement of electrons (negative charge) in a conductor
- Electrons are primary charge carriers in most conductors (metals)
- Electrons flow from negative to positive terminal in a battery-powered circuit
- Direction of electron flow is opposite to direction of conventional current
- Magnitude of current is the same in both cases
Current, Resistance, and Electric Field
- relates current, voltage, and :
- Resistance opposes the flow of electric current in a conductor
- Electric field in a conductor drives the flow of charge carriers
- describes the average speed of charge carriers in response to the electric field
- represents the amount of current flowing per unit cross-sectional area of a conductor
Key Terms to Review (33)
$I = Q/t$: The equation $I = Q/t$ represents the relationship between electric current (I), electric charge (Q), and time (t). It states that the electric current is equal to the amount of electric charge that passes through a given cross-section of a conductor divided by the time it takes for that charge to pass through.
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.
Ampère: The Ampère (A) is the SI unit of electric current, defined as one coulomb of charge passing through a point in one second. It is named after André-Marie Ampère, a pioneer in electromagnetism.
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.
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.
Charge Carriers: Charge carriers are the mobile, electrically charged particles that are responsible for the flow of electric current in a material. They are the fundamental components that enable the conduction of electricity and are central to understanding various electrical phenomena.
Circuit: A circuit is a closed path through which electric current flows, typically consisting of a power source, conductive path, and load. Circuits can be simple or complex, involving multiple components such as resistors, capacitors, and inductors.
Conductors: Conductors are materials that allow the flow of electric current with minimal resistance. They facilitate the movement of charge carriers, such as electrons, making them essential for the operation of electrical circuits, devices, and systems that rely on the efficient transfer of electrical energy.
Conventional current: Conventional current is the flow of positive charge from the positive terminal to the negative terminal of a power source in an electrical circuit. It is a historical convention and opposite to the actual flow of electrons, which move from the negative to the positive terminal.
Conventional Current: Conventional current is a model of electric current flow that assumes the movement of positive charge carriers, such as cations, from the positive terminal to the negative terminal of an electric circuit. This model is widely used in the study of electrical phenomena and is the basis for the majority of electrical engineering principles.
Coulomb: A coulomb (C) is the SI unit of electric charge, representing the amount of charge transported by a constant current of one ampere in one second. One coulomb is equivalent to approximately $6.242 \times 10^{18}$ elementary charges.
Coulomb: The coulomb (symbol: C) is the SI unit of electric charge, named after the French physicist Charles-Augustin de Coulomb. It is a fundamental quantity that describes the amount of electric charge and is used extensively in the study of electric phenomena across various physics topics.
Current density: Current density is a measure of the electric current per unit area of cross-section in a material. It is typically denoted by the symbol $\mathbf{J}$ and has units of amperes per square meter ($A/m^2$).
Current Density: Current density is the amount of electric current flowing through a given cross-sectional area of a conductor. It is a measure of the flow of electric charge per unit area and is an important concept in understanding the behavior of electric currents in various contexts.
Drift velocity: Drift velocity is the average velocity of free electrons in a conductor due to an applied electric field. It is typically very small, on the order of millimeters per second.
Drift Velocity: Drift velocity is the average speed at which charge carriers, such as electrons or holes, move through a conductor or semiconductor under the influence of an applied electric field. It is a crucial concept in understanding electrical current and the behavior of charge carriers in materials.
Electric potential: Electric potential is the amount of electric potential energy per unit charge at a specific point in an electric field. It is measured in volts (V).
Electric Potential: Electric potential, also known as electrostatic potential, is a scalar quantity that represents the amount of work done per unit charge in moving a test charge from an infinite distance to a specific point in an electric field. It is a measure of the potential energy per unit charge at a given location within an electric field.
Electrical current: Electrical current is the flow of electric charge through a conductor, typically measured in amperes (A). It is driven by a potential difference (voltage) across the conductor.
Electrical Current: Electrical current is the flow of electric charge through a conductive material, such as a wire or a circuit. It is the rate at which electric charge passes a given point, and it is measured in amperes (A), the base unit of current in the International System of Units (SI).
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.
Electrons: Electrons are subatomic particles that carry a negative electric charge and are found in all atoms. They play a crucial role in various physical phenomena, including Coulomb's law, electrical current, the motion of charged particles in magnetic fields, and the Hall effect.
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.
Franklin: Franklin is a unit of electric charge in the electrostatic unit (esu) system, equivalent to approximately $3.33564 \times 10^{-10}$ coulombs. Named after Benjamin Franklin, it represents the amount of charge that exerts an electrostatic force of one dyne on an equal charge at a distance of one centimeter.
Free electrons: Free electrons are electrons that are not bound to atoms and can move freely within a material. In conductors, these free electrons enable the flow of electric current.
Ions: Ions are atoms or molecules that have gained or lost one or more electrons, giving them a net positive or negative charge. They are fundamental to the concept of electrical current, as the flow of charged particles, or ions, is what constitutes an electric current.
Ohm's Law: Ohm's law is a fundamental principle in electrical engineering that describes the relationship between the three basic electrical quantities: current, voltage, and resistance. It states that the current flowing through a conductor is directly proportional to the voltage applied across it, and inversely proportional to the resistance of the conductor.
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.
Schematic: A schematic is a graphical representation of an electrical circuit, showing the connections, components, and their arrangement. It uses standardized symbols to represent different electrical devices and connections.
Starter motor: A starter motor is an electric motor that initiates the operation of an internal combustion engine by turning its crankshaft. It converts electrical energy from a battery into mechanical rotation.
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.