Current electricity
What is electric current?
Electric current is the flow of electric charge carriers, usually electrons, through a conductive material.
$$ I=\frac{q}{t} $$
Unit of electric current
The unit of electric current is the ampere (A), which is equivalent to one coulomb of charge passing through a point in a circuit per second.
Direction of flow of electric current
- Conventional current flows from the positive terminal to the negative terminal of a power source.
- Electron flow, which is the actual movement of charge carriers, is from the negative terminal to the positive terminal.
Note : Positive charges consist of protons ( 1.007 amu) and neutrons ( 1.009 amu), both of which are significantly heavier than a free electron ( 0.0005 amu). As a result, the flow of current is primarily determined by the movement of electrons.
Ohm's Law
- Ohm’s Law states that the current (I) flowing through a conductor is directly proportional to the voltage difference (V) across it.
- relationship between current (), voltage (), and resistance ()
Try the simulator below to explore the relationship between the current flowing through a conductor and the voltage applied across it.
What is electric resistance of a material?
Resistance is a measure of the opposition to the flow of electric current through a conductor.
Unit of electric current
The unit of resistance is the ohm (Ω)
What does electrical resistance depends on?
- Material (ρ): Different materials have different intrinsic resistivities.
- Length (L): Resistance is directly proportional to the length of the conductor.
- Cross-sectional Area (A): Resistance is inversely proportional to the cross-sectional area of the conductor.
- Temperature (T): For most materials, resistance increases with temperature.
What is resitivity of a material?
Resistivity (ρ) is a material-specific property that indicates how strongly the material opposes the flow of electric current.
How does resistivity of material depends on temperature?
$$\rho(T) = \rho_0 \left[1 + \alpha (T – T_0)\right]$$