The ammeter to be calibrated is placed in series with a suitable low resistance which may be ï¿½i ohm, ï¿½oi ohm, ï¿½ooi ohm or more as the case may be.
In Germany the work of Martin Ohm (System der Mathematik, 1822) marks a step forward.
An essential accompaniment therefore of the potentiometer is a series of standard low resistances, say of o 1, o oi, o ooi ohm, and also a series of higher resistances divided into known fractions.
981 volt, the strip difference having a resistance of 0.1 ohm, it would be seen that the current passing through the strip was 98 I amperes.
For this purpose a resistance, say, of one ohm is placed in series with the lamp and a resistance of 100,000 ohms placed across the terminals of the lamp; the latter resistance is divided into two parts, one consisting of loon ohms and the other of 99,000 ohms. The potentiometer enables us to measure therefore the current through the lamp by measuring the drop in volts down a resistance in series with it and the potential difference of the terminals of the lamp by measuring the drop in volts down the tooth part of the high resistance of 100,000 ohms connected across the terminals of the lamp.
The standard ohm, sub-standards up to 100,000 ohms, and below 1 ohm to = 1/1000 ohm.
Volta) is defined to be difference of potential which acting between the terminals of a resistance of one ohm sends through it a continuous current of one ampere.
313, P. 80, And Found To Be I.4334 Volts, Assuming The Ohm To Be Correct.
Ohm in 1827, and since known as Ohm's Law.
Ohm (1787-1854) rendered a great service to electrical science by his mathematical investigation of the voltaic circuit, and publication of his paper, Die galvanische Kette mathematisch bearbeitet.
Ohm introduced the clear idea of current strength as an effect produced by electromotive force acting as a cause in a circuit having resistance as its quality, and showed that the current was directly proportional to the electromotive force and inversely as the resistance.
Ohm introduced the definite conception of the distribution along the circuit of " electroscopic force " or tension (Spannung), corresponding to the modern term potential.
Ohm verified his law by the aid of thermo-electric piles as sources of electromotive force, and Davy, C. S.
He followed up the early work of the British Association Committee on electrical units by a fresh determination of the ohm in absolute measure, and in conjunction with other work on the electrochemical equivalent of silver and the absolute electromotive force of the Clark cell may be said to have placed exact electrical measurement on a new basis.