27.1
기전력
기전력(emf)은 전류가 높은 곳에서 낮은 곳으로 흐르게 하는 힘입니다. 잠재적인. EMF가 전혀 힘이 아님에도 불구하고 '기전력'이라는 용어는 역사적인 이유로 사용되었습니다.
정전류를 사용하는 모든 회로에는 EMF 생성 소스가 포함되어야 합니다. EMF 소스의 예로는…
배터리의 발명가인 알레산드로 볼타(Alessandro Volta)는 기전력 또는 emf라는 용어를 만들었습니다.
EMF는 힘이 아니라 배터리의 두 단자 사이의 전위차입니다.
엡실론 기호로 표시되는 EMF는 배터리가 개방 회로에서 전달할 수 있는 최대 전압입니다. 볼트 단위로 표시됩니다.
두 단자 사이에 전선이 연결되면 emf는 음극 단자에서 양극 단자로 전자를 밀어냅니다.
EMF는 터미널을 가로질러 단위 전하를 이동시키기 위해 수행된 작업량으로 정의됩니다.
폐쇄 회로에서 배터리 단자에서 측정된 전압은 항상 emf 값보다 작은 단자 전압으로 정의됩니다. 배터리에 내부 저항 r이 있기 때문입니다.
따라서 단자 전압은 emf와 내부 저항을 가로지르는 전압 강하 간의 차이입니다.
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Q1: Why is electromotive force called a force when it is not actually a force?
The term electromotive force is used for historical reasons, coined by Alessandro Volta, the inventor of the battery. Despite its name, emf is not a force but rather a potential difference between the two terminals of a battery. It represents the maximum voltage a battery can deliver in an open circuit, measured in volts.
Q2: What is the relationship between emf and terminal voltage in a battery?
Terminal voltage is the voltage measured across a battery's terminals when current flows through it, and it is always less than the emf. This difference occurs because the battery has internal resistance. Terminal voltage equals the emf minus the voltage drop across the internal resistance, which increases as the battery depletes.
Q3: How does a battery function as a charge pump in a circuit?
An emf source functions as a charge pump, moving negative charges from the positive terminal to the negative terminal to maintain the potential difference. Work must be done on these charges against the electric field, requiring energy from chemical reactions in the battery. This process raises the charges' potential energy and maintains the high potential at the positive terminal.
Q4: What are examples of devices that produce electromotive force?
Examples of emf sources include batteries, electric generators, solar cells, thermocouples, and fuel cells. All these sources transform energy of some kind—mechanical, chemical, thermal, or other forms—into electric potential energy and send it to the circuit. This energy transformation is essential for maintaining current flow in any circuit.
Q5: How is electromotive force defined in terms of work and charge?
Electromotive force is defined as the amount of work done to move a unit charge across the terminals of a battery. When there is no current flowing, the emf equals the work done on the charge per unit charge. Its unit is the volt, derived from joules of work divided by coulombs of charge.
Q6: What causes the internal resistance of a battery to increase over time?
Internal resistance generally increases as a battery is depleted due to oxidation of the plates or reduction of the acidity of the electrolyte. This increase in internal resistance causes a greater voltage drop across the battery's internal resistance, further reducing the terminal voltage available to the external circuit.
Q7: What happens to electron flow when a wire connects the terminals of a battery?
When a wire is connected between the two terminals, the emf pushes electrons from the negative terminal to the positive terminal through the external circuit. Simultaneously, the battery's internal charge pump moves negative charges from the positive terminal to the negative terminal internally, maintaining the potential difference needed for continuous current flow.