0 a unit for measuring electrical resistance -- ohm
Two 100 ohm resistors in parallel have an equivalent resistance of 50 ohms.
All impedances were maintained below 5000 ohms and were checked before and after testing.
Such a theoretical device would have a zero ohm output impedance in series with the source.
Artifact standards are still used, but metrology experiments relating accurately-dimensioned inductors and capacitors provided a more fundamental basis for the definition of the ohm.
The radiation resistance is typically a fraction of an ohm, making the elementary doublet an inefficient radiator.
A 21 divider probe consists of a 1000 ohm series resistor and a short 50 ohm transmission line.
From 1900 the mercury ohm was replaced with a precision machined plate of manganin.
Values ranged from fractions of an ohm to 22 megohms.
The definition of the ohm unit was revised several times.
