For measurement of force of electric current on the site of the conductor special devices – the ampermeter or a galvanometer are necessary (for definition of small constants and alternating electric currents).
Instruction
1. Force of electric current (I) – the scalar size equal to a charge (q) which proceeds in unit of time (t) through the section of the conductor. According to this definition, force of electric current can be determined on formula I = by q: t.
2. For calculation of current address the law of Ohm defining communication between force of electric current, resistance of the conductor and tension on the site of an electrical circuit. The law of Ohm says that current in the site of a chain (I) is directly proportional to tension (U) and is inversely proportional to the electrical resistance (R) of this site of a chain. In other words, force of electric current is equal to tension relation to resistance. Thus, force of electric current is calculated by formula I = by U: RB to the System International current is measured in Amperes (A).
3. Measurement of force of electric current you ampermetrompodklyuchit the ampermeter to that site of an electrical circuit (conductor) on which you want to measure current. At the same time observe polarity: "+" the ampermeter connect to "+" a current source, and "-" connect it with "-" a current source. Connect the ampermeter to an electrical circuit consistently with that element of a chain which current needs to be measured.
4. For measurement of small constants and alternating electric currents the highly sensitive device – a galvanometer is used. This universal device allowing to determine not only the current, but also tension. To use a galvanometer as the ampermeter, connect the shunting resistor parallel to a galvanometer. The galvanometer is connected to the site of an electrical circuit similar to the ampermeter.