Electric current is the flow of electric charge through a conductor, such as a wire, due to the movement of electrons or other charge carriers.
Conventional current is the hypothetical direction of positive charge flow, opposite to the actual flow of electrons. It is used for ease of understanding and calculation in circuit analysis.
I = q/t => [q = ne]
There are two types of currents:
Direct current is an electric current that flows in one direction only, maintaining a constant polarity over time, commonly produced by batteries or DC power sources.
Alternating current is an electric current that reverses direction periodically, oscillating between positive and negative values, typically used in household electricity supply and generated by alternating voltage sources.
Potential difference, also known as voltage, is the electric potential energy per unit charge between two points in an electric circuit. It drives the flow of electric current.
The potential difference (\(V\)) between two points is calculated using the formula:
\begin{equation} V = \frac{W}{Q} \end{equation}
where,
The SI unit of potential difference is the Volt (V).
Electromotive force is the energy per unit charge supplied by a source, such as a battery or generator, to drive electric current in a circuit. It’s not a force in the traditional sense but rather a potential difference.
The electromotive force (E) is related to the potential difference (V) across the terminals of a source and the internal resistance (r) of the source:
\begin{equation} E = \frac{W}{q} \end{equation}
Where:
( E ) = Electromotive force (Volts, V)
( V ) = Potential difference (Volts, V)
( I ) = Current flowing through the circuit (Amperes, A)
( r ) = Internal resistance of the source (Ohms, Ω)
SI unit of EMF is Volt (V).
Ohm’s Law states that the current flowing through a conductor is directly proportional to the voltage across it, at a constant temperature.
Ohm’s Law is mathematically represented as:
\[I = \frac{V}{R}\]
Where:
( I ) = Current flowing through the conductor (Amperes, A)
( V ) = Voltage across the conductor (Volts, V)
( R ) = Resistance of the conductor (Ohms, Ω)
Ohm’s Law assumes constant temperature, while resistance can change with temperature.
It does not apply to materials that don’t follow a linear V-I relationship.
It doesn’t consider time-varying circuits or transient effects.
At very low voltages, contact resistance and nonlinearities can affect accuracy.
Not suitable for complex circuits with nonlinear elements.
Not valid for high-frequency AC circuits due to capacitance and inductance effects.
Doesn’t account for components like diodes or transistors.
Not applicable to nonuniform materials where resistance varies along the length.