Resistance Versus Inductance – Plus Why it Matters to Technicians

What is the difference between resistance and inductance and why does it matter to a technician?

Resistance and inductance are both properties of electrical circuits that affect the behavior of electrical components and the flow of electrical current. The main difference between them is that resistance is a measure of the opposition to the flow of electrical current caused by the material the wire is made of, while inductance is a measure of the opposition to the change in the flow of electrical current caused by the presence of an electromagnetic field.

Resistance is measured in ohms (Ω) and is a constant value for a given material at a given temperature. It determines how much current will flow through a circuit for a given voltage. High resistance in a circuit can cause the circuit to overheat or not function properly.

Inductance, on the other hand, is measured in Henries (H) and is a property of electrical components such as inductors or coils. Why is “H” used for conductance? It was named after at least one of the people who discovered it, Joseph Henry. See “The Discovery of Inductance” for more information.

Inductors resist changes in the flow of current, so they can be used to smooth out fluctuations in voltage or current in a circuit. Inductance can also cause delays in the flow of current through a circuit, which can affect the timing of the circuit.

For a technician, understanding the difference between resistance and inductance is important because it can help them troubleshoot problems in electrical circuits. For example, if a circuit is not functioning properly, a technician may need to measure the resistance of the components in the circuit to determine if there is a problem with a particular component. Alternatively, if there is a timing issue with a circuit, the technician may need to consider the inductance of the circuit to determine if it is causing a delay in the flow of current.

The Discovery of Inductance

The concept of inductance was discovered independently by two scientists, Joseph Henry in the United States and Michael Faraday in England, in the early 19th century.

Joseph Henry, an American physicist and inventor, discovered the phenomenon of electromagnetic induction in 1831, which is the basis of inductance. He demonstrated that a changing magnetic field can induce an electric current in a nearby conductor. Henry was also the first to coil wire into a coil, which he called an “electromagnetic helix,” and observed that the electromagnetic effect was stronger in a coil than in a straight wire.

Michael Faraday, an English scientist, also discovered electromagnetic induction independently of Henry around the same time. He performed a series of experiments in the early 1830s that led to the discovery of the basic principles of inductance, including the concept of magnetic flux and the induced electromotive force (EMF) in a conductor.

Both Henry and Faraday are considered pioneers in the field of electromagnetism and their work laid the foundation for the development of modern electrical technology.

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Inductors and resistors are a very important part of all electronics and electric circuits. HVAC service technicians must know the basics of both to be super-star HVAC service technicians.