Michael Faraday is probably best known for his law of induction. But he also discovered the Faraday Effect in 1845 which states that light and electromagnetism are related phenomena. Faraday asserted that, in fact, light is a form of electromagnetism, anticipating James Clerk Maxwell by nearly two decades. Faraday stated that when a solid or […]

## Does Kirchhoff’s Voltage Law really fail?

Gustav Kirchhoff (1824-1887) was an accomplished Prussian physicist and instrument maker, and best known for his current and voltage circuit laws. Kirchhoff’s first circuit law, known as his current law, states that the algebraic sum of currents in a network of conductors meeting at a point is zero. Kirchhoff’s second circuit law, known as his […]

## What is Fourier transform IR spectroscopy?

Most EEs probably think of a Fourier transform in terms of an operation that converts time-based waveforms on a scope into their component frequencies. But Fourier transforms also play a role in infrared spectroscopy. It might be easiest to explain Fourier transform infrared spectroscopy by contrasting it with conventional spectroscopy. Also called “dispersive spectroscopy,” the […]

## The difference between VSWR and the S_{11} reflection coefficient

A traveling signal along an electrical transmission line reflects back toward the source when one or more events occurs: One or both of the conductors is open at the far end (receiving end). The conductors are shorted at the far end (very common). There is a discontinuity in the characteristic impedance or an electrical fault […]

## Electric charge and instruments used to measure it

Many devices have been built for measuring electric charge. One of the first was the gold-leaf electroscope. When a charged object touches the metal knob at the outer end of the rod, the charge flows down to the leaves. The leaves diverge due to the repulsion of like charges they have received. The degree of […]

## What’s all this double-slit photon stuff?

Newton’s corpuscular theory of light was the accepted model of light propagation in the 17th and 18th centuries. The double-slit experiment, first performed by Thomas Young in 1801, seemed to revive the wave theory of light. In the modern version of this experiment, a coherent light source such as a laser is aimed at an […]

## When oscillators didn’t contain op amps

Examine a discrete oscillator circuit today and you’ll likely find an operational amplifier with components in a feedback loop that cause the oscillation. In many cases, oscillators implemented with op amps are updated versions of designs that formerly used odd-ball components such as neon bulbs and delay lines to get the required phase shift needed […]

## The difference between amplifier gain and antenna gain

Amplifier and antenna gain may sound the same, and both may be expressed in decibels, but they actually are measures of two different things. In an amplifier, gain is simply the ratio of the output divided by the input. Gain has no units as it is a ratio. However, amplifier gain is often expressed in […]

## Going parabolic: The difference between a Ronchi, Foucault, and a Caustic test

Amateur astronomers like to build their own telescopes, sometimes to the point of even grinding the objective mirrors. This is doable, but involves purchasing the mirror blank plus various grades of grinding abrasives, polishing compounds and specialized tools. The lens must have a precise parabolic profile. It takes special test instruments to figure out whether […]

## What’s all this triplen harmonics stuff?

Unless your background is in ac power, it’s possible you haven’t run into the term triplen harmonic. Triplen harmonics have to do with the third harmonic. Even-numbered harmonics do not normally exist in power systems due to symmetry between the positive and negative halves of the ac cycle. It is the odd-numbered harmonics that engineers […]