Ohm's Law or not Ohm's Law... That is the question

[CocaCola]

A VIP member with over 1000 posts and can't apply Ohms law to an inductor? Oh boy, we're in a whole heap o' trouble. Bet we had some good answers there.

If you bothered to actually read the thread the argument revolves around the definition of what Ohm's Law is defined as, not necessarily it's application and formulating an answer that can be applied to it...

Is it simply...

I = V ÷ R

or

When you don't have a true resistance are you allowed to estimate and/or derive at a theoretical resistance by the use of additional equations or whatever, and still call it Ohm's Law?

 

[CDRIVE]

Someone remind me about this thread when I next tell people they need to understand Ohms Law and that it's pretty trivial

After Bob's last post I did a search "AC Ohms Law Origins". I was hoping to attribute a name in connection with Z concepts. According to Wiki, It seems to fall under Maxwell's Equations.

Ohms law states that the voltage and current are proportional. They are not in an inductor, capacitor, transistor, diode, neon light, triac, diac SCR. So if you are agreeing with the statement that I challenged, "All components obey Ohm's law", you have a lot of work to do.

Bob

For Inductors and Capacitors, they are but 90° out of phase.

As for the other components listed In there you have to factor in the context in which I made that statement. If you recall I was working with a young fellow building a 12AU7 amplifier. Note that I said "governed", not "obey".

Originally Posted by Solidus
I was asking if plate-load resistors have an analog in transistor-mediated circuits.

(solidus)

Sure they do. For BJT's it's the "Collector Resistor". It doesn't matter if we're talking Tubes, BJT's, MOSFETs, JFETs, Resistors, Light Bulbs, Inductors, Capacitors or even Wire. All components in an electronics circuit are governed by Ohms Law.

Chris

That statement was made in the following context:

An Instructor draws a BJT (Q1) amplifier on the black board. It includes an Emitter Resistor (Re), Collector Resistor (Rc), Base to GND Resistor (Rbg) and a Base to Vcc Resistor (RbVcc). The instructor gives the class the value of only one Resistor, the Emitter Resistor (Re) = 100R. The Instructor then writes the following on the board Vcc = 12V, Q1(hFE) = 100, Ic = 5mA, Vc = 6V. Solve for the values of Rc, Rbg, RbVcc. I_Rbg = 10 x Ib.

These students will most definitely utilize their new found skills with Ohms Law to solve this class work. In the end the behavior of Q1 is most definitely governed by Ohms Law.

There may exist a component that I can't spin into an Ohms Law scenario like this but, off hand, I can't think of one.

Chris

 

[Genup]

In my teaching career, I've seen many students that always ask these types of questions in physics class and my reply was always " understand the ohm's law wheel " and you'll get your answer. Although, it was asked about ten years ago, but for viewers and readers, it'll be beneficial.

 

[Harald Kapp]

@Genup : No use reviving threads that are a few years old.
Thread from 2012 -> closed