Instruments {ammeter}| can measure currents.
Instruments {galvanometer}| can measure small currents and current direction.
Instruments {ohmmeter}| can measure resistance.
Instruments {potentiometer}| can measure voltages at zero current, as ratio to exactly known voltage.
Instruments {voltmeter}| can measure electric potentials.
Devices {Wheatstone bridge}| can find resistance or capacitance in circuits using ratios. Wheatstone bridges eliminate voltage effects. AC current negates overall flow effects.
Current from a potential source P splits between two known resistances, R1 and R2, which have a galvanometer G across their endpoints to measure current and voltage (Figure 1). From one endpoint is an adjustable resistance Rv. From the other endpoint is an unknown resistance Rx. The resistances Rv and Rx meet at a point. If the ratio of the adjustable resistance Rv to the first known resistance R1 equals the ratio of the unknown resistance Rx to the second known resistance R2, the galvanometer has zero voltage and current.
For typical resistances, one can set R1 = R2, so Rv = Rx at galvanometer zero current and voltage.
If three resistances are known and one unknown, the measured voltage allows calculating the unknown resistance.
Wheatstone bridges can also find capacitance.
5-Physics-Electromagnetism-Circuit-Kinds
Outline of Knowledge Database Home Page
Description of Outline of Knowledge Database
Date Modified: 2022.0225