Electric Charge and Current

Electric Charge:

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field.

There are two types of charge
         -positive charge(carried by proton)
         -negative vharge(carried by electron)



Properties:

• electric charge is conserved property.

                       ${\displaystyle \scriptstyle \partial V}$ ${\displaystyle \mathbf {J} \cdot \mathrm {d} \mathbf {S} =\int J\mathrm {d} S\cos \theta =I.}$

Thus,
                
The charge transferred between times  and  is:
               

• electric charge is carried by subatomic particles.
• charge is quantized.

                          e = 1.602×10⁻¹⁹ coulombs

• electric charge creates an electric field.

Units:
The SI unit of quantity of electric charge is the Coulomb.


   1 coulomb = 6.242×10¹⁸ e (e is the charge of proton)

 The coulomb  is defined is defined as the quantity of charge that has passed through the cross section of an electrical conductor carrying one ampere within one second.

         -The quantity of electric charge can be directly measured with an electrometer, or indirectly                   with an ballaistic galvanometer.
       
         - The unit Faraday is sometimes used in electrochemistry
              1 Faraday = 96485.33256

Electric Current:

An electric current is a flow of electric charge.

In electric circuit charge is carried by moving electrons in wire. It can also carried by ions in an electrolyte, or by both ions and electrons such as in ionised gas(plasma).

The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter.

Alternating Current:

Alternating current (AC)is an electric current which periodically reverses direction.

The usual waveform of AC in most electric power circuit is sine wave. Audio and Radio signals carried on electrical wire s are also example of alternating current.

Alternating current are accompanied by alternating voltage. An AC voltage can be described as function of time by following equation.

                              ,
                                   where,
                                    is the peak voltage
                                    is the angular frequency
                                         .
                                    is the time

Direct Current:

The direct current(DC) is the unidirectional flow of electric charge. A battery is an example of DC power supply.

DC can be obtained from AC by use of rectifier and also DC can be converted into AC by using inverter or motor-generator set. Direct current is used to charge battery and as a power supply for electronic system.                     

Difference:

S.N.		Alternating Current	Direct Current
1	The amount of energy that can be carried	It is safe to transfer over longer city distances and will provide more power.	Practically the voltage of DC cannot travel very far until it begins to lose energy
2	The cause of the direction of flow of electron	It is denoted rotating magnet along the wire.	It is denoted steady magnet along the wire.
3	Frequency	The frequency of alternating current will be either 50Hz or 60Hz depending upon the country.	The frequency of direct current will be zero.
4	Direction	It reverses its direction while flow in a circuit.	It only flows in one direction in the circuit.
5	Current	It is the current of magnitude which is varying with time.	It is the current of constant magnitude.
6	Flow of electrons	Here electrons will keep switching the direction forward and backward.	Electrons move steadily in one direction or forward.
7	Obtained from	The source of availability is AC Generator and mains.	The source of availability is either cell or battery.
8	Passive parameters	It is impedance.	It is resistance.
9	Power Factor	It basically lies  between 0 and 1	It will be always 1
10	Types	It will be of different types like sinusoidal, square, Trapezoidal, and triangular.	It will be of pure and pulsating.