Wiktor Wise
Electrical flow, or electric current, is the movement of electric charge through a conductor or space. It is measured in amperes (A), which is the equivalent of one coulomb per second. Electric current can be measured with an ammeter, which detects the magnetic field associated with the current. The d'Arsonval meter is a type of ammeter that uses a coil of wire and a permanent magnet to measure the current. The size of conductors, fuses, and components will determine the amount of current flowing through a circuit.
| Characteristics | Values |
|---|---|
| Definition | A flow of charged particles, such as electrons or ions, moving through an electrical conductor or space |
| Charge Carriers | Electrons, ions, or holes |
| SI Unit | Ampere (A) |
| Other Names | Amperage |
| Measurement Devices | Ammeter, galvanometer, d'Arsonval meter, digital multimeter |
| Measurement Method | Indirect measurement of voltage across a precision resistor using Ohm's Law |
| Voltage Sources | Batteries, DC generator |
| Voltage and Current Relationship | Voltage provides the necessary pressure to cause electrons to move, resulting in an electric current |
| Resistance Unit | Ohm |
| Alternating Current (AC) Waveform | Sine wave, triangular wave, or square wave |
| Direct Current (DC) | Unidirectional flow of electric charge |
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What You'll Learn
Electric current is the flow of charged particles
In electric circuits, the charge carriers are often electrons moving through a wire. These electrons follow an erratic path, bouncing from atom to atom, but generally drifting in the opposite direction of the electric field. The speed of this drift can be calculated mathematically. Typically, electric charges in solids flow slowly. For example, in a copper wire of cross-section 0.5 mm^2, carrying a current of 5 A, the drift velocity of the electrons is on the order of a millimetre per second.
In solids such as wires, the positively charged carriers are immobile, and only the negatively charged electrons flow. Because the electron carries a negative charge, the electron current flows in the opposite direction of the conventional (or electric) current. When solving electrical circuits, the actual direction of the current through a specific circuit element is usually unknown. Consequently, each circuit element is assigned a current variable with an arbitrarily chosen reference direction. When the circuit is solved, the circuit element currents may have positive or negative values. A negative value means that the actual direction of the current through that circuit element is opposite to the chosen reference direction.
There are several methods of measuring electric current. The most common method is to perform an indirect measurement of the voltage across a precision resistor and use Ohm's law to measure the current across the resistor. Current can also be measured using a device called an ammeter, which is based on electromagnetics and is associated with the early moving coil (d'Arsonval) meter.
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The SI unit for measuring electric current is the ampere
Electric current refers to the flow of electric charge through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. The moving particles are called charge carriers, which may be one of several types of particles, depending on the conductor. In electric circuits, the charge carriers are often electrons moving through a wire.
The ampere was named after French physicist and mathematician André-Marie Ampère (1775-1836), who studied electromagnetism and laid the foundation of electrodynamics. The unit was established as a standard for electrical measurement at the 1881 International Exposition of Electricity. The definition of the ampere has evolved over time, and in the 2019 revision of the SI, it was defined by fixing the elementary charge e to be exactly 1.602176634 x 10^-19 C, which is approximately 6.241509074 x 10^18 elementary charges moving in a second.
Electric current can be measured using an ammeter, which is based on the theory of electromagnetism or Ohm's law. The d'Arsonval meter is a type of ammeter that uses a coil of wire and a permanent magnet to measure the current. Other methods of measuring current include detecting the associated magnetic field or performing an indirect measurement of the voltage across a precision resistor.
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Current can be measured using an ammeter
Current is the flow of electric charge through a circuit, and it is measured in amperes (amps). The SI unit for measuring electric current is the ampere (A), which is equal to a flow of one coulomb of charge per second.
There are two main types of ammeters: in-series and induction. In-series ammeters are wired directly into the circuit, while induction ammeters detect the current by clamping a ring around a wire, which reads the current through the electromagnetic field given off by the electricity.
When using an in-series ammeter, it is important to first test the internal fuse of the ammeter. Most ammeters have two leads: an input (+) and an output (-). If the resistance rating is low, the fuse is good. It is also important to set the ammeter current type and range. If the ammeter has multiple settings, choose the highest setting to prevent blowing the meter's internal fuse if the amperage is too high.
When measuring the current, break the circuit open and connect the ammeter's test probes to the two points of the break. If the meter is manually ranged, select the highest range for current, then move the selector switch to lower range positions until the strongest indication is obtained without over-ranging. If the meter indication is backward (left motion on an analog needle or negative reading on a digital display), reverse the test probe connections and try again.
Induction ammeters work by clamping a ring around the power input wire, which reads the current through the electromagnetic field. It is important to locate the negative (-) terminal for the power source, as the wire running between this and the item being powered is the power input line.
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Current can be direct or alternating
Electric current is the flow of electric charge and is measured in amperes, or amps. The SI unit for measuring electric current is the ampere (A), which is equal to a flow of one coulomb of charge per second. Electric current can be measured with an ammeter, also known as a d'Arsonval meter.
There are two types of electric current: direct current (DC) and alternating current (AC). In a direct current system, electric charge moves in only one direction and the voltage remains constant. Direct current is found in almost all electronics and is produced by batteries.
In contrast, alternating current refers to a system in which the movement of electric charge and voltage periodically reverses direction. AC is the form of electric power most commonly delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave, although certain applications use alternative waveforms such as triangular or square waves.
AC is easier to transform between voltage levels, making it more suitable for long-distance power transmission. On the other hand, DC is more suitable for energy storage in devices such as batteries and capacitors. In some cases, AC from an outlet needs to be converted into DC for use in electronic devices.
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Current flows when voltage causes electrons to move
Electric current refers to the flow of charged particles, such as electrons or ions, through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. This flow of electric charge is measured in amperes, or amps (A), which is equivalent to one coulomb per second.
In electric circuits, the charge carriers are typically electrons moving through a wire. These electrons are negatively charged and follow an erratic path, bouncing from atom to atom. However, they generally drift in the opposite direction of the electric field. The speed of this drift can be calculated mathematically.
The movement of electrons in a particular direction is caused by electromotive force, or EMF, which is also known as voltage. Voltage is measured in volts. It is the force that creates "electrical pressure," pushing electrons in a certain direction within a conductor. When a voltage source or EMF is removed, the current ceases to flow.
In a metal wire connected to a DC voltage source, such as a battery, the source places an electric field across the conductor. This electric field influences the free electrons of the conductor, causing them to drift toward the positive terminal. Thus, the free electrons become the current carriers in a typical solid conductor. The presence of an electric field is essential for the flow of electrons or electric current.
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Frequently asked questions
A measurement of electrical flow is called an electric current.
Electric current is the flow of electric charge through a conductor or space.
Electric current is measured in amperes (A) using a device called an ammeter.
An ammeter is an instrument used to detect and measure electric current. A d'Arsonval meter is a type of ammeter that uses a coil of wire and a permanent magnet to measure the current.
