Resistance Definition and 1000 Threads

Starting from this Fall of potential method, earth ground resistance measurement of a ground electrode E driven into the ground can be done using the "Fall of potential method". Such a measurement method involves two auxiliary test probes (say S and H) driven into the ground at a certain...

Hi, I would like someone to test the superconductor I have come up with or let me know how ( I don't have a lab ), what I can say that the resistance is almost zero with my Fluke.Regards

This is a THEORETICAL thought exercise ONLY to help in understanding the concept of parallel vs series. If I were to have a copper bar of uniform density as a conductor. One end of the bar is at potential A, the other end of the bar is potential B. Lets say the copper bar has a resistance of...

Fundamentally I'm struggling with the premise of the problem. Once I get that I think the math of solving the problem will be straight forward. But like I said I think the problem is fundamentally unsound. I hope to be proven wrong. initially there is no current in the lower branch of the...

I understand that removing bulb E will cause the equivalent resistor to change in the circuit. This change will cause the current across the circuit to change (which will either brighten or dim the bulbs). I found that R_eq (with E) is 1.167. R_eq = [1 + (1/1+1)]^-1 + [1 + 1]^-1 = 1.167 I...

I have plotted the V-R graph. when Rv is 600 ohms, Rf is also 600ohms, which means the voltage across both resistors should be split evenly at 3V each since batt is 6V. however, from the graph, i noticed that Vf is 3.4V and Vv is 2.6V instead at 600 ohms. i would like to know where did it...

So , max power is dissipated when the load resistance and thevenin resistance becomes equal such that $$P\leq \frac{V_{\text{th}}^2}{4R_{\text{th}}}$$ Then i applied the 'star delta' transformation by converting the 'delta' ABC to 'star' ABC . From there , by loop current method , i got...

Let's say the elements connected in parallel have voltage drop of ##V_x'## each , hence they should have the same resistance ##R_x'##as per the conditions of the problem (since it mentions that if voltage drop across an element is less than ##1## or greater than ##1## , it has some constant...

I wanted to find the differential form of the above equation and i get $$\frac{dR(t)}{dt}=R_{0}\alpha$$ (##t_{0}##=0 degree celsius) So $$\alpha=\frac{dR(t)}{dt} \frac{1}{R_{0}}$$ (##\alpha##= temperature coefficient of resistance ##R_{0}##=Resistance at temperature 0 degree celsius) This idea...

Building a DIY kayak simulator training machine. A rope is tied to each end of a broomstick and runs around a resistance wheel, guided by a system of seven pulleys . The machine works exactly as intended. But I feel there is too much drag. Trying to see how I can reduce the drag,in the...

Hi Friends! Regard the 2 kW electric kettle and 60 W incandescent bulb - what happens if we plug them in series? It is the problem I often ask my students somewhere at the end of the term to check if they remember basic "laws" about electricity. Recently I started collecting some exercises on a...

So assuming this wire is probably not ideal since its used in a real life situation, theres possible resistances in the wire before the faulty point as well as after the faulty point. Theres also resistance connecting the faulty point and the ground. Now does current stop flowing in the wire...

Hi Physics Forum Folks! What an amazing resource of knowledge, ... thanks! The question is on the attached graphic, as its much more clear with an illustration. (Please read questions on this graphics first before looking at the video below,) This video is a very quick look at the actual...

I've been really confused on how electricity and circuits work 1. If eletrons "slow down" inside a resistor (or wire, I'm considering it's resistance to be ≠ 0) because of collisions with the lattice, then wouldn't the electrons pile up? The charges accumulating doesn't seem to be good. 2. Some...

In your 2 diabetes insulin secretion is present, but it is ineffective. It means that the circulating insulin is unable to push all the glucose into cells. They call it insulin resistance. But at the same time, if synthetic insulin is injected or insulin-secreting drugs are given, they seem to...

I have a lot of doubts regarding this . Let's say the resistance is ##R## where the net interaction force becomes zero . So , the current flowing should be : $$i=\frac{V_{\circ}}{R}$$ Will charges be induced like in capacitors? If yes then let's say ##\pm q## is induced and the length of the...

For a consumer with a resistance of 2 ohms, it has an internal resistance of 0.3 ohms and a voltage of 130 Vwe switch on the power source. The resistance of each connecting thread is 0.15 ohms. What is the voltage drop on the line and what is the terminal voltage?

The first thing I thought about was the relationship ##\vec{J}=\frac{\vec{E}}{\rho_r}## which is a statement of Ohm's law. That is, current density is proportional to electric field and the constant of proportionality is the reciprocal of resistivity ##\rho_r##, which is the same as...

Hi what factors determine the resistance and inductance in a coil and they related i.e. if the resistance is high would the inductance be high ? Additionally, would the resistance and inductance value change over time? I only ask this as we tested the resistance and inductance on our coils...

The reading on the voltmeter is 0. I figure the potential drop through line AB must be the same as the potential drop through AC (since voltmeter is zero). As such, the 10 Ohm resistor has the same as the effective resistance of the parallel branch. 1/10 = 1/8 + 1/R 1/R = -0.025 R = -40 Ohms...

good morning gentlemen, I would like to ask you a fairly simple question but which I am unable to resolve. Then considering the "skin effect", which involves an increase in resistance to the passage of current with consequent generation of eddy currents, this leads to an accumulation of charges...

Just a few quick questions regarding airflow, mostly in connection with motors creating the airflow, like pc fans, vacuum motor, air going into a car engine through air filter, etc. 1) Adding more filters increases the availably surface through which the air can flow, therefor reducing the...

My calculation: ##400=\left(\frac{9.9}{\sqrt{2}}\right)^2 R## and I got R = 8.2 ohm But the answer key used Io (9.9 A) instead of Irms Why? Thanks

Hi, I am not sure if I have calculated the task here correctly: Based on the drawing, I now assumed that the two resistors are connected in parallel. The total resistance can then be calculated as follows ##\frac{1}{R_T}=\frac{1}{R_1}+\frac{1}{R_2}##. Since the two wires are made of the same...

Currently when set to 1C, the fridge cools to and maintains 4-5C(As a conversion when set to 34f it cools and maintains approx. 40f. ), all functions like fan/defrost are working correctly. Potentially the main board has an issue but all other zones are working correctly so I would prefer to not...

TL;DR Summary: I have to find an equivalent resistance of the circuit below, dependent on the amount of ##R_3## - resistors. Here is the circuit: I think there is no general solution. When I want to calculate it, I have to do...

In a recent thread, I thought I understood what was going on but alas, I am still confused. So I offer this diagram and ask for more help please. Shown is an aircraft holding pattern. The one on the left is flown in still air. The one on the right is flown with a wind coming from the...

a. The resistance thermometer bridge circuit shown in FIGURE 1 has a designed maximum temperature of 200°C, ignoring the effects of connecting wire resistance. If the connecting loop is 250 m determine the smallest gauge (swg) of copper wire which must be used if the indicated maximum...

It shows 0 and it's obvious why. I have another question. Can I say that in this circuit the current is maximum and it equals to ##\frac ε r = 2A##?! Someone asked me this question: Are A and B two ends of the wire? If yes, Why is there current in the wire even though the potential difference...

Why meter bridge is chosen over post office box to measure low resistance?

I'm trying to understand the load-resistance of an A123 Nanophosphate High Power Lithium Ion cell. https://www.buya123products.com/uploads/vipcase/844c1bd8bdd1190ebb364d572bc1e6e7.pdf My understanding is that resistance increases as the cell charges. The datasheet says "Internal Impedance...

I would think that it is 2 A (6/3 because there are three wires the current can go to), but this does not seem to be correct.

What is it's benefit?

I'm struggling to find the exact way to do this and think that I am overthinking the equation, all of my lesson notes tend to explain how to find the armature resistance using the back e.m.f and the armature current, we can figure out the armature current but do not have enough information to...

Continue reading...

How is the load (variable resistance) adjusted in an automobile battery? Mechanically (potentiometer, rheostat) or electronically (digital potentiometer) or are both configurations possible.Can the load in a automobile battery be a three terminal divider (potentiometer) or is it almost always...

Hi, What is the formula or methodology for finding the Crr? There are many of those tests done on the internet, but none state the procedure of calculation. I'm trying to find the correlation between tire pressure and distance and want to use Crr as one of the key factors influencing it. Maybe...

How do we correctly do resistance ie. spot weld by use of arc or TIG welder (if the difference is big explain each of this weld separately) to join piled up two bolt rings of the same thickness 2-2.5 mm and center diameters but largely different outer diameters

Is there a way to obtain equation 9.42 (I is current, j is current density, and sigma is conductivity) in the following image (from Modern Electrodynamics by Andrew Zangwill, the part on electromotive force) besides using V=IR and substituting the line integral of j/conductivity for V? The...

I don't understand what the gamma letter in the equation is supposed to represent.

Why is resistivity inversely proportional to resistance for NTC semiconductors?

Good evening, I have a question on the problem I've provided in the homework statement. Essentially, the problem is asking us to compare the maximum height and time to max-height between a simple projectile motion case vs. a case using fluid resistance proportional to v. I've solved everything...

I thought the one with more mass would fall faster

hi, in recent science projects I have been studying the effect of water on electrical resistance of materials that absorb water such as wood and sponge (the reason for the majority of my weird questions regarding water and electricity). I am calculating resistance by reading the current going...

Hi I have been wondering what is the difference between resistance force and friction coefficient. While doing research online I could not find a clear answer. Maybe someone here will now:bow: