In electricity, electric current abroad+us department of commerce current refers to electric current, which is the flow of electrons. Lightning is an example of an electric current, as is the solar wind, the source of the polar aurora. Probably the most familiar form of electric current circuit elements are connected current electric flow cell is the flow of conduction electrons in a metallic wire. This is how utility companies deliver electricity. In electronics, electric current is most often the flow of electrons through conductors and devices such as resistors, handheld electric current sensor but it is also the flow of ions inside a battery or the flow of holes within a semiconductor.
Relation between current and charge
The symbol typically used for the amount of current sodium battery electric current (the amount of charge Q flowing per unit of time t) is I, from the German word Intensität, which means 'intensity'.
Formally this is written as
- or inversely as
Conventional current
Conventional current was defined early in the history of electrical science as a flow of positive charge. electric motor current In solid metals, like wires, the positive charges are immobile, and only the negatively charged electrons flow in the direction opposite conventional current, but this is not the case in most non-metallic conductors. In other materials, charged particles flow in both directions at the same time. Electric currents in electrolytes are flows of electrically charged atoms (ions), which exist in both positive and negative varieties. For example, an electrochemical cell may be abdominal excersizer electric current constructed with direct current electric motor salt water (a solution of sodium direct current electric motors chloride) on one side of a membrane and pure water on the other. The electric current abroad membrane lets the positive sodium ions pass, but temperature electric current not the circuit current electric flow cell connected elements wires negative chlorine ions, so a net current results. Electric currents in plasma are flows electric current flow of electrons as well as positive and negative ions. In ice and in certain solid electrolytes, flowing protons basic electric current constitute simple definition of electric current the electric current. To electric wire current capacity by gauge simplify this situation, the original definition general electric and current initiatives of conventional current still stands.
There are also instances where the electrons are the charge that is physically moving, but electric circuit current flow cell where it makes more a definition of an electric current sense to think of the current as the movement of positive "holes" (the spots that should have an electron to current state of the electric industry make the conductor electric circuits current flow cell neutral). This is the case in a p-type semiconductor.The SI unit of electrical current is the kevco electric current projects ampere.
Electric current is therefore sometimes informally referred to as amperage or ampage, by analogy with the term electric current through glass ball voltage. Though this is a valid term, some electric current for the distributed network devices engineers electric tools, electric current through salty water direct current frown on it.
The speed of an electric current
The charged particles current electric whose movement causes an electric current do not electric plug current international always move in straight lines. In metals, for example, they follow an erratic path, bouncing from atom to atom, but generally drifting in the direction of the electric field. The speed at which they drift can be calculated from the equation:
- I = nAvQ
where
- I is the current
- n is number of charged particles per unit volume electric current for the remote device
- A is the cross-sectional area of the conductor
- v is the drift velocity, and
- Q is the charge on each particle.
- n is number of charged particles per unit volume electric current for the remote device
For example, in a copper wire of cross-section electric current for the metro ethernet 0.5 mm², carrying a current of 5 A, the drift velocity of the electrons is of the order of a millimetre per second. To take a different example, in the near-vacuum inside a cathode ray tube, the electrons travel in near-straight lines ("ballistically") at about a tenth of the speed of light.
However, we know that an electric signal travels much faster than this; usually close to the speed of light. These fungus electric current results show that the speed of the charged particles is not necessarily related to the speed of the electric signal. To understand how signals travel faster than the particles that carry them, it is necessary to understand the properties of electromagnetic waves (see article).
Current density
Current density is the current per unit (cross-sectional) area.
Mathematically, current is defined as the net flux through an area. Thus:
where, in the MKS or SI system of measurement,
- I electric current massage is the current, measured in amperes
- j is the "current density" measured in amperes per square metre
- A is the area through which the current is flowing, measured electric current learning cycle in square metres
- j is the "current density" measured in amperes per square metre
The current density is defined as:
where
- n is the particle density (number of particles per unit volume)
- x is the mass, charge, or any other characteristic whose flow one would like to measure.
- u is the average velocity of the particles in each volume
- x is the mass, charge, or any other characteristic whose flow one would like to measure.
Current density is an important consideration in the design of electrical and electronic systems. Most electrical conductors have electric current experiments with kids plant root electric current a finite, positive basics of electric current resistance, making them dissipate power in the form of heat. The current density electric wire direct current capacity by gauge must be kept sufficiently low to prevent the 3phase electric current conductor from melting or burning up, or the insulating material failing. In superconductors, excessive current density may generate a strong enough magnetic field to cause spontaneous loss of the superconductive property.
Electromagnetism
Every electric current produces a magnetic field. The magnetic field can be visualized as a pattern of the physics of electric current circular field lines surrounding the wire.
Electric current can be directly electric current flowing through computer's federal pacific electric current limiter case measured with a galvanometer, but this method involves breaking the circuit, which is sometimes inconvenient. Current can also be measured without breaking the circuit by detecting the magnetic field it creates. Devices used for this include Hall effect sensors, current clamps and Rogowski coils.
Ohm's law
Ohm's law predicts the current in an (ideal) resistor (or other ohmic electric current device) to be the quotient of applied voltage over electrical resistance:
where
- I is the current, measured in amperes
- V is electric plug current isreal the potential difference measured in volts
- R is the resistance measured in ohms
- V is electric plug current isreal the potential difference measured in volts
Electrical safety
The danger of an electric shock depends on the current (in milliamperes), electric current measurement duration and the current's path in the body:
- 1 mA causes a tingle
- 5 mA causes a slight shock
- 50 to 150 mA may result in death, e.g. through rhabdomyolysis (muscle breakdown) and resultant acute renal failure
- 1-4 A causes ventricular fibrillation
- 10 A causes cardiac arrest (only at this current will a typical home fuse break the circuit)
Currents through the heart and the nervous system are the most dangerous. As most dangerous sources are voltage sources, the current present depends on the resistance of the body between the points of contact current capacity of electric wires and any current limiting built into the source.
The comparison between the dangers of alternating current general current information electric boat ct and direct current has been a subject of debate ever since the War of Currents in the 1880s. DC tends to cause continuous muscular contractions that make the victim electric current and turning sand to glass hold on to a live conductor, thereby increasing the risk of deep tissue burns. On the other hand, mains-frequency AC tends to interfere more with the heart's electrical definition of electric current pacemaker, leading to an increased risk of fibrillation. electric current and switches definitions AC at higher frequencies holds a different mixture of can your ntural human electric current show up on an ohmeter hazards, such as RF burns and the possibility of tissue damage with no immediate sensation of pain.
See mycelial growth electric current also
- Alternating current
- Direct current
- electrical conduction for more information on the physical mechanism of current flow in materials
- SI electromagnetism units
External links
- Online Current Converter - convert between various units of current, such as ampere, biot, abampere, statampere, and so on
- Interactive Current Conversion Table - convert selected unit to all other units of current
- Which direction does electricity really flow?
Back to the top of Electric current.
Provided by wikipedia.org
Electronics Topics
The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The design and construction of electronic circuits to solve practical problems is part of the fields of electronic engineering, and the hardware design side of computer engineering. The study of new semiconductor devices and their technology is sometimes considered as a branch of physics.
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