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

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**Electrical resistance:**

$R=\frac{\rho l}{A}$

Where,

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

$J=\sigma E$

J = current density

E = electric field applied

The other form of Ohm's law is

$J=\sigma E$

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**

- $\overrightarrow{{v}_{d}}$ is defined as the velocitâ€¦

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