one of the oldest branches of science without which we cannot just imagine
ourselves in the current world. The rate of flow of charge through a conductor
is termed the electric current and is measured in ampere. The
potential difference across the conductor causes the charge flow between them.
The potential difference is measured in volt and is the work done in moving a unit positive charge between two points in an electric field.
It implies that one joule per coulomb is one volt. In circuits potential
difference is measured using a voltmeter and the current by an ammeter.
The current flow from a high potential area to a low potential area is termed
the conventional current whereas the flow of electrons constitute the
electron current and is in a direction opposite to that of the conventional
electricity, we have two categories of materials, namely conductors and
insulators. All of the conductors do not conduct electricity the same way. Some
of them offer a restriction to the flow of charge and are referred to as
resistors. The restriction to the flow of charge is electrical resistance and depends on the physical dimensions and temperature of the conductor. The
resistance (R) of a conductor varies directly with its length (l) and
inversely with its area of cross-section (A). The mathematical
expression is where ‘r’ is the
constant called resistivity or specific resistance of the material which depends on the nature and temperature of the material. Resistivity is
measured in ohm-metre.
At a given temperature, the current through
a conductor is directly proportional to the potential difference across its
ends and is known as Ohm’s law.