What is electric current?
Electric current is the flow of electrical charge through a conductive medium in relation to time.
When there is a potential difference between two points in a conductive medium,
the electrical charge begins to flow from the point of higher potential to the point of lower potential in order to equalize the charge
distribution between the points. The rate of charge as a
function of time is called electric current.
electric Current formula
If q the electrical Coulomb charge is transferred between these two times t sec,
the current can be calculated as
In differential form,
current can be represented by
Unit of electric Current
Since current is the ratio of the charge transferred to the time required for that charge transfer,
we can say that a unit of current is such a rate of charge transfer that a
Coulomb charge is transferred from point to point. another in a second.
Hence the unit of current is the coulomb / second and is known as the ampere after
the great physicist Andrew Marie. It is the SI unit of electric current.
Theory of Electricity
Current in Metallic Conductor
The main cause of the current through a metallic substance is the flow of electrons, ie the directional drift of the free electrons.
In metal there are many free electrons in the metallic crystal structure even at room temperature.
If the electrical potential differs between two points in the metal, the free electrons that moved randomly in the equilibrium potential state,
as well as the free electrons supplied by the source (if a source is connected between these two points)
are now due to electrostatic attraction to a higher one Potential point driven.
Since each of the electrons has a negative charge of – 1.602 × 10 – 19 coulombs, we can say that the negative charge is moving to the higher potential point. The flow rate of this negative charge as a function of time is the current in the metal.
Conventional Direction of electric Current
Although the electron flow or negative charge is from a point of lower potential to a point of higher potential,
the conventional current direction is considered from a higher potential to a lower potential.
Although the current is mainly caused by the flow of electrons, that is,
the flow of negative charge,
it was previously believed that the electric current is due to the flow of positive change.
However, it has now been proven that the current in a metallic conductor is due to an electron flow or negative charge,
but the direction of the current is still considered to be opposite to the
The current direction viewed from a higher potential point to a lower
potential point is known as
the conventional current direction.
Types of Current
When the present flows during a constant or fluctuating direction, the present is
named DC .
When the present flows alternately in both directions, a frequency is named AC . The mean of an AC is zero.
The AC is measured within the effective value.
one among the most parameters of AC is frequency.
Magnetic Effect of Current
When current flows through the conductor, a magnetic current surrounds the conductor. The direction of the ball line of the magnetic
flux is often determined
using the right rules.
If we imagine that we have the current-carrying driver between our
right and the thumb in the direction of the current, four fingers on our right point in the direction of the ball line of the magnetic flux.
If we make a coil with a conductor and current flows through the coil, a total magnetic field will surround the coil due to the magnetic action of each conductor in the coil.
Here we can also determine the direction of the field using the right hand rule.
If we hold the live coil with our four fingers along the current direction in the turns of the coil, the extended thumb shows the direction of the magnetic field.
Current in Magnetic Field
When we bring a current-carrying conductor or coil into a magnetic field, a mechanical force acts on the current-carrying conductor or coil.
This mechanical force depends on the current flowing through the conductor or coil.
Measurement of Current
Current can be measured according to the principle of the interaction between current and magnetic field.
One of the basic instruments used to measure current is the pmmc instrument, or the permanent magnet moving coil instrument. The pmmc instrument can only measure direct current. Alternating current can be measured by moving an iron instrument in
magnetic field created by the current through the instrument coil causes a piece of soft iron to move by either attraction or repulsion.
This instrument can also measure direct current.
Rectifier instruments are also used to measure alternating current. Here the bridge rectifier is used to rectify the alternating current,
then it is measured with
a pmmc instrument.
Regardless of the type of ammeter, all ammeters are called ammeters. An ammeter is always connected in series, with its path the current to be measured.
If very high currents need to be measured,
we use current transformers to reduce the current for measurement purposes.
Heating Effect of Current
When current flows through a conductor there is a thermal effect in the conductor.
The power loss in the conductor is i2R watts. The energy loss is i2Rt joules.
This loss of energy is
converted into heat.
This is called Joule’s
law of heating.