Classification of Material—

Conductor—

The material which conduct electric current fairly well are called conductor.

Insulator—

The material which do not conduct electric current are called insulator.

Semiconductor—

These are the materials whose resistivities lie in between those of conductor and insulator.

Carriers of Current—

The charged particles which by flowing in a definite direction set up an electric current are called current carriers.

Current density—

The current density at any point inside a conductor is defined as the amount of charge flowing per sec through a unit area held normal to the direction of the flow of charge at that point.

Conductance—

The conductance of a conductor is the ease with which electric charges flow through it. It is equal to the reciprocal of its resistance and is denoted by ‘G’.

Resistance—

The resistance of a conductor is the property by virtue of which it opposes the flow of charge through it.

It is equal to the ratio of the potential difference applied across the conductor to the current flowing through it.

Its unit is Ohm or Volt/Ampere.

Definition of One ohm—

If      V=1 Volt         i=1 Amp    then

R= 1 ohm

Electromagnetic Force—

The emf of a source is equal to the maximum potential difference between its terminals when it is in open circuit that is when it is not sending any current in the circuit.

The emf of a source is defined as the energy supplied by the source in taking a unit positive charge once round the complete circuit.