Fisika electric current

Fisika
electric current


today I am posting again the subject of physics. As for the material that is an electrical current. I'd just learned
 An electric current is the amount of electrical charge resulting from the movement of electrons, flowing through a point in an electric circuit per unit time. [1] An electric current can be measured in units of Coulomb / second or amperes. [1] Examples of electric currents in everyday life ranging from very weak in units mikroAmpere (\ mu A) as in the tissues of the body to a very strong current 1 -200 kiloAmpere (kA) as occurs in lightning. [2] [3] in most circuits of direct current resistance can be assumed to be a constant electric current is so large current flowing in the circuit depends on the voltage and resistance in accordance with Ohm's law. [1 ]

Electric current is one of the seven basic units in international units. [4] The international unit for electric current is the Ampere (A). [4] formally defined as a unit of Ampere constant current which, if maintained, will produce a force of 2 x 10 - 7 Newton / meter between two straight parallel conductors, the cross-sectional area that can be overlooked, within 1 meter of each other in a vacuum. [4]
For constant current, the current I in amperes can be obtained by the equation

where I is the electric current, Q is the electric charge, and t is the time (time).

While in general, the electric current flowing at any given time are: [6]

To determine the total amount of charge transferred in the period 0 to t through the integration of: [5]

In accordance with the above equation, the electric current is a scalar quantity because both the charge Q and time t is a scalar quantity. [5] In many ways it is often portrayed electric current in a circuit using the arrow keys, [5] one of them as in the diagram above. The arrows are not vectors and vector operations do not need. [5] In the diagram above show the current flowing through the two branches and flows out through two other branches. Since the electric charge is conserved, the total electric current that flows out should be the same as the electric current flowing into [5] so 
Arrows indicate direction of flow only flow along the conductor, not the direction in space. [5]
Flow direction

In the diagram depicted arrows in the direction of movement of the flow of positively charged particles (positive charge) or called the conventional flow. [7] positive charge carriers will move from the positive pole of the battery toward the negative pole. [5] In fact, the charge carriers in an electrically conductive particles are negatively charged electrons are driven by the electric field to flow opposite direction to conventional current. [5] Unfortunately, for reasons of history, use the following convention: [5]

     The arrows in the direction of the flow is described movement of charge carriers should be positive, despite the fact that the charge carriers are negatively charged and move in opposite directions. [5]

Such conventions can be used in most circumstances it can be assumed that the movement of positive charge carriers have the same effect with a negative charge carrier movement. [5]
current density

Current density (English: current density) is the flow of charge in a given cross-sectional area at any point the conductor. [5] In SI, the current density has units of amperes per square meter (A/m2). [5]

where I is the current in the conductor, J is the current density vector that has the same direction with the velocity of the charge if the positive charge and the opposite direction if the negative charge, and dA is a vector element wide perpendicular to the elements. [5] If the electrical current uniform along the surface and parallel to dA then J is also uniform and parallel to dA so the equation becomes: [5]

Soo

where A is the total cross-sectional area and J is the current density in units of A / m
speed of drift

When a conductor is not passed an electric current, the electrons in it moving randomly with no net movement in any direction as well. [5] Meanwhile, when an electric current flows through a conductor, the electrons keep moving randomly, but they tend to drift along the conductor in the opposite direction the electric field produces a flow of current. [5] the speed of drift (English: drift speed) in a conductor is small compared to the speed of random movement, which is between 10-5 and 10-4 m / s compared to about 106 m / s on a copper conductor.