PHYSICAL QUANTITY

Electrical resistance: formulas and units of measurement

Electrical resistance: symbol R, unit Ohm. Formulas and explanations for Electricity, Oscillations and waves.

R

\text{Om}

ohm

KEY CONNECTIONS

Formulas

R = \frac{U}{I}

R = U / I

R = ρ \frac{l}{S}

R = ρl / S

X_{L} = 2 π ν L

Xᴸ = 2πνL

X_{C} = \frac{1}{2 π ν C}

Xᶜ = 1 / (2πνC)

R = R_{0} (1 + α t)

R = R₀(1 + αt)

NOTATION

$R$: Electrical resistance is a measure of a conductor's resistance to electric current.
$U$: Electric voltage is the work done by the electric field when transferring a unit charge.
$I$: Current strength is the charge passing through the cross section of a conductor per unit time.
$\rho$: Resistivity is a characteristic of a material’s ability to resist current.
$l$: Conductor length is the length of the conductor section under consideration.
$S$: Area is the size of a surface or cross section.
$X_L$: Inductive reactance is the resistance of the coil to alternating current.
$\nu$: Frequency is the number of repetitions of a process per unit of time.
$L$: Inductance is the ability of a conductor to create a magnetic field when current passes.
$X_C$: Capacitance is the resistance of a capacitor to alternating current.
$C$: Electrical capacity is the ability of a conductor or capacitor to accumulate charge.
$R_0$: Initial resistance - resistance at the selected initial temperature.
$\alpha$: Temperature coefficient is a characteristic of the change in resistance when heated.
$t$: Temperature is a measure of the thermal state of the body.

THEORY

PRACTICE