27.10
전류계
전류계는 전류를 측정하는 도구입니다. 회로에서는 A 기호로 표시됩니다. 전류계는 전류를 측정하기 위해 장치 또는 구성 요소와 직렬로 배치됩니다. 직렬 연결은 직렬로 연결된 물체에 동일한 전류가 흐르기 때문에 사용됩니다. 회로에 여러 개의 저항기가 있고 각 저항기에서 전…
전류계는 회로의 전류 값을 측정하는 데 사용되는 도구입니다. 전류를 측정해야 하는 요소와 직렬로 연결됩니다.
이상적인 전류계는 저항이 0이지만 실제 전류계는 유한하지만 무시할 수 있는 저항을 가지고 있습니다.
저항이 무시할 수 없는 경우 회로의 전류계는 회로의 등가 저항을 변경하고 측정되는 전류를 수정합니다.
모든 검류계는 션트 저항을 병렬로 추가하여 전류를 측정하는 데 사용할 수 있습니다.
병렬 연결된 션트 저항기는 전류를 분할하므로 검류계가 전체 범위 편향 전류보다 몇 배 더 큰 DC 전류를 측정할 수 있습니다.
필요한 션트 저항은 검류계의 전체 변형 전류 및 코일 저항의 알려진 값을 사용하여 결정됩니다.
이것은 검류계의 전압 강하와 션트 저항을 동일시하여 수행됩니다.
여기서, Ia는 병렬 조합을 통과하는 총 전류이고, Ia 마이너스 Ifs는 션트 저항을 통과하는 전류입니다.
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Q1: Why is an ammeter connected in series with a circuit component?
An ammeter measures current and must be connected in series because objects in series have the same current passing through them. This placement ensures the ammeter reads the actual current flowing through the component without bypassing it, providing an accurate measurement of the circuit's current flow.
Q2: What happens if an ammeter has significant resistance in a circuit?
If an ammeter's resistance is not negligible, it changes the circuit's equivalent resistance and modifies the current being measured. An ideal ammeter has zero resistance, but real ammeters have finite resistance. To avoid measurement errors, ammeters are designed with negligible resistance, typically a fraction of a milliohm.
Q3: How many ammeters are needed to measure current in series versus parallel resistors?
For two resistors in series, a single ammeter is needed because current is identical through both. For two resistors in parallel, three separate ammeter readings are necessary: one for the battery current and one for each resistor's current. The number of ammeters depends on the circuit configuration and measurement requirements.
Q4: How can a galvanometer be converted into an ammeter?
A galvanometer can measure current by adding a shunt resistance in parallel with it. The parallel shunt resistor divides the current, allowing the galvanometer to measure DC currents several times greater than its full-scale deflection current. The required shunt resistance is determined by equating voltage drops across the galvanometer and shunt resistor.
Q5: What is the relationship between shunt resistance and galvanometer current capacity?
The shunt resistance is calculated using the galvanometer's known full-scale deflection current and coil resistance. By placing a shunt resistor in parallel, the total current divides between the galvanometer and shunt. This allows measurement of larger currents while protecting the galvanometer from excessive current that would damage it.
Q6: Why do ammeters typically contain a fuse?
Since current in a circuit travels through the ammeter, it contains a fuse to protect the meter from damage caused by excessively high currents. The fuse acts as a safety device, breaking the circuit if current exceeds safe levels and preventing internal damage to the ammeter's sensitive components.
Q7: How does ammeter placement affect measurements in circuits with multiple resistors?
Ammeter placement depends on circuit configuration. In series circuits, one ammeter measures the same current through all components. In parallel circuits, multiple ammeters are needed to measure total current and individual branch currents. Proper placement ensures accurate current measurement without altering the circuit's equivalent resistance or affecting household wiring and electrical safety.