Definition:
An electric current is a flow of electric charge through an electrical conductor. Electric
charge flows when there is voltage present across a conductor.
In electric circuits this charge is often carried
by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons.
Electric
currents cause many effects, notably heating, but also induce magnetic fields,
which are widely used for motors, inductors and generators.
Formula:
Formula for determining the current
is given by,
I=Q/t
Where,
I= current
Q=charge
t=time
Unit:
The SI unit of electric current is
coulomb /second which we call as
ampere.
One ampere is the flow of electric charges through a surface at the rate
of one coulomb per second.
Electric
current can be measured using an ammeter .
AC and DC current
:
In alternating
current (AC, also ac), the movement of electric charge periodically reverses direction.
Direct current (DC) is the unidirectional flow of electric charge. Direct current is
produced by sources such batteries, solar cells, etc.
Origins of AC and DC
current
:
A magnetic field near a wire causes electrons to
flow in a single direction along the wire, because they are repelled by the negative
side of a magnet and attracted toward the positive side. This is how DC
power from a battery was born, primarily attributed to Thomas Edison's work.
AC generators gradually replaced Edison's DC battery
system because AC is safer to transfer over the longer city distances and can
provide more power. Instead of applying the magnetism along the
wire steadily,
scientist Nikola Tesla used a magnet that was rotating. When the magnet was
oriented in one direction, the electrons flowed
towards the positive, but when the magnet's orientation was flipped, the electrons turned
as well
Similarities and
differences between AC and DC current:
Alternating Current
|
Direct Current
|
|
Amount of
energy that can be
carried:
|
Safe to transfer over longer
city distances and can provide more power
|
Voltage of DC cannot travel very far until it begins to lose energy
|
Flow of Electrons:
|
Electrons keep switching directions- forward and backward
|
Electrons move
steadily in one
direction or 'forward'
|
Cause of the direction of flow of electrons:
|
Rotating magnet along the wire
|
Steady magnetism along the wire
|
Frequency:
|
The frequency of alternating currents 50Hz or 60Hz depending upon the
country.
|
The frequency of direct current is zero.
|
Direction:
|
It reverses its direction while flowing in a circuit
|
It flows in one
direction in the circuit
|
Current:
|
It is the current of magnitude varying with time
|
It is the current of constant magnitude
|
Types:
|
Sinusoidal, Trapezoidal, Triangular, Square
|
Pure and pulsating
|
Passive Parameters:
|
Impedance
|
Resistance only
|
Passive Parameters:
|
Impedance
|
Resistance only
|
