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Probably everyone reading this article already has education on elementary circuit analysis (CA) and many of us are much more advanced. Typically, the basic course covers both circuits covers simple devices like R, L, and C, it mentions electric or magnetic fields and then moves on to Ohm’s Law and CA… However, few such courses…
Introduction In a previous article on measuring battery internal resistance, a simple technique for low-resistance measurement was outlined. In this article, the technique has been modified and expanded somewhat although the basic method remains the same. It is about as simple as it gets – one passes current through a reference resistor in series with…
Abstract Richard Pierce describes the intention of his book [2] about associative algebras as his attempt to prove that there is algebra after Galois theory. Whereas Galois theory might not really be on the agenda of physicists, many algebras are: from tensor algebras as the gown for infinitesimal coordinates over Graßmann and Banach algebras for…
Introduction A commonly encountered school-level Physics practical is the determination of the internal resistance of a battery – typically an AA or D cell. Typically this is based around a simple model of such a cell as a source emf in series with a small resistor. The cell is connected to a resistive load and…
If you are interested in programming and electronics, you probably do not need an introduction to Arduino. If you want to make your Arduino projects permanent, then it is a good idea to use solo microcontrollers rather than Arduino boards in the final setup. While Arduino boards are great for prototyping, buying an Arduino board…
Introduction We show how one can solve most if not all, introductory-level projectile motion problems in one or maybe two lines. To this end, we forgo convention. We demote clock time ##t## to a parameter of secondary importance and ditch the independence of motion in the vertical and horizontal directions. Starting from the first principles,…
Note: It is assumed that the reader has read part I of the series. Introduction The ambiguity and flaws discussed in part I can be resolved using the law of conservation of energy. In the words of Richard Feynman, There is a fact, or if you wish, a law, governing all natural phenomena that are…
Introduction In a previous Insight, A New Interpretation of Dr. Walter Lewin’s Paradox, I introduced the fact that there are two kinds of E fields. One (Em) is generated whenever a source of emf is produced. The other (Es) is the electrostatic field. The Es field always terminates on free charges; the Em does not. …
What is bloatware? When you unbox your new phone, it comes with Android which is pre-installed by the manufacturer. This is termed “stock firmware”. Stock firmware also comes with several apps pre-installed, like native browser, Google apps, games, etc. Some applications are manufacturer-specific. For example, many Samsung phones come with Samsung Health and Galaxy Apps…
Definition/Summary The impedance of a load (a combination of components) in an AC current is a complex number [itex]Z\ =\ R+jX[/itex] where [itex]R[/itex] is the resistance of the load and [itex]X[/itex] is its reactance. It can also be written in polar form: [itex]Z\ =\ |Z|e^{j\phi}[/itex], or as the phasor [itex]|Z|\angle\phi[/itex]. Impedance is the AC equivalent…
As a university teacher and as a PF member, I have often noted that students are largely unaware of or not using dimensional analysis to help them in their pursuit of knowledge or to check their results. Several recent threads on PF have also highlighted this issue. The intent of this Insight is therefore to…
The electric power industry faces much turmoil in the coming decades. The business model of the electric utility company (public or private) may not survive. In addition, the power needs of high-density cities may diverge significantly from non-urban areas causing political turmoil and technical hurdles. The increasing share of renewable energy will be a major…
Much has lately been said regarding this paradox which first appeared in one of W. Lewin’s MIT lecture series on ##{YouTube}^{(1)}##. This lecture was recently critiqued by C. Mabilde in a second YouTube video and submitted as a post in a PF ##{thread}^{(2)}##. The latter cited the third source, that of K. T. McDonald of…
We asked our PF Advisors to tell us their most memorable or influential textbook and why. Here are their responses… Thanks to all the PF Advisors that shared their favorite textbook. We have more questions for them in the near future. Stay tuned for another “Ask the Advisors”!
Please give us a bit of background into your educational and professional life. I’m a public school kid through and through. After going to the local high school where I grew up in Westford, Massachusetts, I attended Michigan State University to get Bachelors degree in astrophysics (with several extra classes in Computer Science). From snowy…
Give us a little background on Jim Hardy Born and raised in Miami Florida of parents with roots in Springfield Missouri . So at heart i’m a small town midwestern fellow. Miami was small in the 1950’s but it became cosmopolitan and outgrew me. I spent a career working in the nuclear plant south of…
This article is geared towards: I’ve never owned a camera, but I want to get a ‘real’ camera (that doesn’t cost too much). I’ve owned an entry-level camera already and I want to take the next step. A: Usually called ‘bridge cameras’, ‘prosumer cameras’, or ‘micro cameras’, these cameras will allow you to have manual…
Introduction First, congratulations! Camera technology has advanced to the point where a complete novice, using an entry-level camera right out of the box, can take photos that (under certain circumstances) appear identical to professional photos. Regardless if you only use your camera in the ‘automatic’ setting or if you explore the art of photography, the…
At first, I wanted this title to say “Ohm’s law is not a Law.” But someone else used that phrase in a recent PF thread, and a storm of protest followed. We are talking about the relationship between the Voltage between two points in a circuit and the current between those same two points. ##R=V/I##,…
Power system security is much too big a topic for this article. But I can squeeze in a few points about vulnerability to cyber attacks. First, this topic follows naturally from Part 2’s discussion of grid control (remember that flyball governor?). Second, I feel that’s apropos in an era where the public believes that…
Is it possible to design an unbreakable cipher? Do methods of encryption exist that guarantee privacy from even the most capable and highly-resourced of prying eyes? This question is especially relevant today, as individual privacy and national security increasingly find themselves at opposite ends of the arbitration table. Powerful nation-states with unparalleled mathematical know-how and…
Let me use the terms “power grid” and “network” interchangeably. What is the Power Grid Required to Do? Deliver energy to customers, and thereby earn money so that the utilities can profit. Deliver power wherever and whenever the customers demand it. That implies maintaining the dynamic balance between energy produced, energy lost, and energy…
Instantaneous Power The formula for power is: ##P=V\cdot I## , power= voltage*current. We call that, instantaneous power. Even when ##V## and ##I## are changing in time, ##P=V\cdot I## applies for each instant. It matters not if the ##V## or ##I## changes are `sinusoidal, what their frequency is, or even if they are aperiodic. ##P=V\cdot…
We are proud to introduce you to Mathematical Physicist and PF member John Baez! Give us some background on yourself. I’m interested in all kinds of mathematics and physics, so I call myself a mathematical physicist. But I’m a math professor at the University of California in Riverside. I’ve taught here since 1989. My wife Lisa…
Can you give us a brief history of berkeman? I grew up in a military family (my dad was an Army colonel), so we moved all over the place when I was a kid, finally settling in Calistoga in the northern part of the Napa Valley, California, for my high school years. Being a military…
Resistance to complex math seems to never die out. I see it frequently in PF posts. Often it takes the form of challenges rather than questions. First challenge: Complex is just a mathematical trick that has nothing to do with physics. Second challenge: Everything that complex does can be accomplished by ordinary real numbers. My…
A long time ago I read a paper in the IEEEProceedings recounting the history of the superheterodyne receiver. Overall it was a very interesting and informative article, with one exception: in it, the author remarked that the modulation (or mixing) principle was nothing new, and is already known to piano tuners who traditionally used a…