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Current Electricity

Electric Current (I)
• It is the rate of flow of electric charge flowing though any section of wire.
Ohm’s Law
• Electric current flowing through a conductor is directly proportional to the potential difference across the two ends of the conductor; physical quantities such as temperature, mechanical strain, etc. remaining constant.
V = RI
Where, R is a constant for a given conductor
Electrical resistance:
$R=\frac{\rho l}{A}$
Where, r is the specific resistance or electrical resistivity of the material

Conductance and Electrical conductivity:
•   Conductance $G=\frac{A}{\rho l}$
• Electrical conductivity (s) is defined as the reciprocal of resistivity.
$\sigma =\frac{1}{\rho }$
The other form of Ohm's law is

J = current density
E = electric field applied
Motion of electrons due to thermal energy

• Free electrons are in continuous random motion. They undergo change in direction at each collision and the thermal velocities are randomly distributed in all directions.
• Average thermal velocity,$u=\frac{{u}_{1}+{u}_{2}+{u}_{3}+........+{u}_{n}}{n}$ is zero … (1)
•
Drift velocity
• $\stackrel{\to }{{v}_{d}}$ is defined as the velocit…

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