Electric current

An electric current is a flow of electric charge. The equation of current is: [1]

is the current flowing
is the change in electric charge
is the change in time

The SI unit of electric current is the ampere (A). This is equal to one coulomb of charge in one second. Current can be found in wires, batteries, and lightning.

The source of current

In conducting materials, some electrons are very loosely bound to the atoms of the material. When large amounts of these atoms come together, there is a sort of electron cloud that "hovers" near the atoms of the material. If you examine a cross-section of the piece of conducting material, the electrons will move very quickly through it. This motion is caused by temperature, and electrons flowing in one direction tend to equal the electrons flowing from the other direction, so this is not what causes current to flow. Electrons flow from one atom to another, a process has been compared to the passing of water buckets from one person to another in a bucket brigade. [2]

When an electric field is put on the wire, the electrons respond almost instantly by drifting slightly in the opposite direction of the field. They gain energy from the field, which is lost very quickly when they bump into other electrons in the material. As long as the field is in place, however, the electrons will gain back that energy that they lost, and the process will continue. This "jolt" that electrons receive from the electric field is the source of current, not the overall flow of electrons themselves. From this discussion, we can see two things that current is not:

  • It is not an actual "flow" of electrons in the everyday sense of the word: If we examine the speed given to the electrons by the field, it is usually very small, on the order of millimeters per second. It would take half an hour for electrons to cross a 10-foot (3 m) room at this rate. Since a light bulb flips on almost immediately after hitting the switch, something else must be at work.
  • It is also not a "domino effect", although this analogy is closer than the flow. Since electrons are so tiny, even when they are moving very quickly they are not being propelled by great force..
Other Languages
Alemannisch: Elektrischer Strom
العربية: تيار كهربائي
azərbaycanca: Elektrik cərəyanı
Bân-lâm-gú: Tiān-liû
башҡортса: Электр тогы
беларуская: Электрычны ток
беларуская (тарашкевіца)‎: Электрычны ток
Esperanto: Elektra kurento
한국어: 전류
Ido: Korento
Bahasa Indonesia: Arus listrik
interlingua: Currente electric
íslenska: Rafstraumur
עברית: זרם חשמלי
қазақша: Электр тогы
Kiswahili: Mkondo wa umeme
Kreyòl ayisyen: Kouran elektrik
lietuvių: Elektros srovė
македонски: Електрична струја
Malagasy: Rianaratra
മലയാളം: വൈദ്യുതധാര
მარგალური: ელექტრული დენი
Bahasa Melayu: Arus elektrik
မြန်မာဘာသာ: လျှပ်စီး
Nederlands: Elektrische stroom
日本語: 電流
нохчийн: Ток
norsk nynorsk: Elektrisk straum
oʻzbekcha/ўзбекча: Elektr toki
ਪੰਜਾਬੀ: ਬਿਜਲਈ ਕਰੰਟ
پنجابی: کرنٹ
Piemontèis: Corent elétrica
português: Corrente elétrica
Qaraqalpaqsha: Elektr togı
română: Curent electric
slovenščina: Električni tok
ślůnski: Sztrům
српски / srpski: Електрична струја
srpskohrvatski / српскохрватски: Električna struja
Basa Sunda: Arus listrik
татарча/tatarça: Электр агымы
українська: Електричний струм
اردو: برقی رو
ئۇيغۇرچە / Uyghurche: توك ئېقىمى
Tiếng Việt: Dòng điện
吴语: 电流
粵語: 電流
中文: 电流