Current and Resistance

The SI unit of electric current is the ampere (A), which is defined as the flow of one coulomb of charge per second.

Ohm's Law states that the current flowing through a conductor is directly proportional to the voltage applied across it, and inversely proportional to the resistance of the conductor.

Ohm's Law is expressed mathematically as $I = V/R$, where $I$ is the current, $V$ is the voltage, and $R$ is the resistance.

The SI unit of resistance is the ohm ($\Omega$), which is defined as the resistance of a conductor that allows a current of one ampere to flow when a voltage of one volt is applied across it.

The resistance of a conductor is directly proportional to its length ($L$) and resistivity ($\rho$), and inversely proportional to its cross-sectional area ($A$).

For most metals, the resistance increases with increasing temperature due to the increased thermal agitation of atoms, which hinders the flow of electrons.

Reactance is the opposition to the flow of alternating current (AC) in a circuit caused by the energy stored in the electric and magnetic fields.

The reactance of a capacitor ($X_C$) is given by the formula $X_C = 1/(2\pi fC)$, where $f$ is the frequency and $C$ is the capacitance.

The reactance of an inductor ($X_L$) is given by the formula $X_L = 2\pi fL$, where $f$ is the frequency and $L$ is the inductance.

Impedance is the total opposition to the flow of current in a circuit, which includes both resistance and reactance.

The impedance ($Z$) of a circuit is given by the formula $Z = R + jX$, where $R$ is the resistance, $X$ is the reactance, and $j$ is the imaginary unit.

Impedance is the ratio of the voltage across a component to the current flowing through it.

The unit of impedance is the ohm ($\Omega$), which is the same as the unit of resistance.

Power consumed by a circuit is inversely proportional to its impedance.

The power ($P$) consumed by a circuit is given by the formula $P = I^2R$, where $I$ is the current and $R$ is the resistance.