Electricity[part=2] class=10

SOME IMPORTANT DEFINITION

Static and current electricities:

Static electricity deals with the electric charges at rest while the current electricity deals with the electric charges in motion.

                  Conductor:

 A substance which allows passage of electric charges through it easily is called a
‗conductor‘. A conductor offers very low resistance to the flow of current. For Example- copper,silver, aluminium etc.

                    Insulator:

A substance that has infinitely high resistance does not allow electric current to flow through it. It is called an ‗insulator‘. For example -rubber, glass, plastic, ebonite etc.

                 Electric current:

The flow of electric charges across a cross-section of a conductor constitutes an electric current. It is defined as the rate of flow of the electric charge through any section of a conductor.     Electric currentharge/Time or I = Q/t Electric current is a scalar quantity.

                 Ampere:

It is the S.I. unit of current. If one coulomb of charge flows through any section of a conductor in one second, then current through it is said to be one ampere.

1 ampere = 1 coulomb/1 second    or      1 A = 1C/1s = 1C^s-1
1 milliampere =   1 mA = 10^-3 A
1 microampere = 1µA = 10^-6 A

                   Electric circuit:

The closed path along which electric current flows is called an ‗electric circuit‘.

Semiconductors

Those substances, whose conductivity is between that of insulators and conductors called semiconductors.

Semiconductors are more poor conductors than metalic conductors but better conductors than insulators.

EX=Germanium,Silicon.

ELECTROSTATICS;

The branch of physics which deals with charges at rest and interaction among them is called electrostatics.

SOME NUMERICAL RELATED TO CURRENT

[1]=The filament of an electric lamp draws a current of 0.4 ampere,which lights for 3 hours.Calculate the amount of charge.

[2]=Find current when 100 million electrons flow through a cross section of conductor in one microsecond.

[3]=Current through a wire is 5 milliampere.Find the ammount of charge which will pass through this wire in 10 sec.Also find,how many electrons will pass through it.

[4]=Find current through a wire if 100000000000 electrons pass through a wire in 0.01 sec.