Electrical resistance

Electromagnetism
Electricity · Magnetism · Magnetic permeability
Electrostatics Electric charge • Coulomb's law • Electric field • Electric flux • Gauss's law • Electric potential energy • Electric potential • Electrostatic induction • Electric dipole moment • Polarization density
Magnetostatics Ampère's law • Electric current • Magnetic field • Magnetization • Magnetic flux • Biot–Savart law • Magnetic dipole moment • Gauss's law for magnetism
Electrodynamics Lorentz force law • emf • Electromagnetic induction • Faraday’s law • Lenz's law • Displacement current • Maxwell's equations • EM field • Electromagnetic radiation • Liénard–Wiechert potential • Maxwell tensor • Eddy current
Electrical Network Electrical conduction • Electrical resistance • Capacitance • Inductance • Impedance • Resonant cavities • Waveguides
Covariant formulation Electromagnetic tensor • EM Stress-energy tensor • Four-current • Electromagnetic four-potential
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The electrical resistance of an electrical conductor is a measure of the difficulty of passing an electric current through a substance. It explains the relationship between voltage and the current. With more resistance in a circuit, less electricity will flow through the circuit. The inverse of resistance is conductance, a measure not much used. All objects have some resistance, except superconductors.

Resistance, discovered by Georg Simon Ohm in 1827, is the ratio between voltage and current. Ohm's law said that the voltage between any two points in a conductor changes directly as the current between the two points, given the temperature remains the same. He described it with the equation:

${\displaystyle R={\frac {V}{I}}}$

which models the ratio, where:

${\displaystyle R}$ is the resistance of the object, measured in ohms (Ω)

${\displaystyle V}$ is the voltage across the object, measured in volts (V)

${\displaystyle I}$ is the current going through the object, measured in amperes (A)