Current Definition and 1000 Threads

In a certain anisotropic conductive material, the relationship between the current density ##\vec j## and the electric field ##\vec E## is given by: ##\vec j = \sigma_0\vec E + \sigma_1\vec n(\vec n\cdot\vec E)## where ##\vec n## is a constant unit vector. i) Calculate the angle between the...

Could someone please help. i need to connect a 12vdc motor which can draw 16 amps to a switch that has an led on it. the led is rated at 3v 20mA. The power supply i am using is rated to put out 12vdc at 30A I thought of the possibility of adding a resistor to the positive pole of the led. In...

Consider a circuit with a witch, capacitor and an AC voltage source. The sinusoidal AC voltage source is depicted in the following graph: We know that, ##Q = CV## ##\frac{dQ}{dt} = C \frac{dV}{dt}## ##i = C\frac{dV}{dt} \tag{1}## So from the graph, the voltage increases rapidly around ## t =...

I am struggling with the angles. Since the conducting wire is moving down for it to be stand still, the force should be opposing it, hence the current should be from Right to Left. I am confident of the Force direction and its value is if ## I ## is the current ##F = ILB (N)## since L and B...

https://www.physicsforums.com/attachments/267955 I think i should apply kirchkoff rules so I can find i1,i2,i3 R1,R' but I don't have enough information and I don't know how to have those informations .What is your ideas?

Hi all, Managed to get an answer out, but unfortunately, it doesn't correspond with the answer given ( –3.09 A) Would appreciate if one could check out what I did wrongly here: ## V_{1}=2\times 5=10V ## At node 2: ## \dfrac{V_{1}-V_{2}}{2}=12+\dfrac{V_{2}}{1}+\dfrac{V_{2}-V_{3}}{2}## We can...

Disclaimer: The solution to this question has already been posted by my instructor. I made this post to understand why my solution is wrong or if the instructor is wrong, since their explanation does not make sense to me. My reasoning: Using the fact that the magnetic torque on a...

The problem seems to be easy but i don't get the correct answer. a. The current in the field coils. The net resistance of Rf = 106 and Rr = 5.9 is ## Reff = \frac {(106 * 5.9)} {(106.9 + 5.9)} = 5.54 ## ## \frac { 120 - E} {5.9} = 4.82 => E = 91.562 ## ## If = \frac { 120 - 91.562} {106} =...

##\vec \tau = \vec \mu \times \vec B -eq1## ## F = I \vec l \times \vec B -eq2 ## The forces i have indicated The magnetic moment is coming out of the page. I am only attempting only the part (a) as of now a. The force calculations are F1 = 1.4*0.22*1.5 = 0.462 +X direction F2 = 1.4*0.22*1.5...

I am studying the theory of force on a current carrying conductor in a uniform magnetic field, the Force is ## F=ILB##. I am slightly confused here let us say the conductor is placed in the uniform magnetic field ##B##, then if the current is passing through the conductor then that current would...

Good afternoon guys, I was making some researches about building my own EV and its' specifications but I have a few no direct answered questions and some of them I humbly ask the help for you guys, based on the configuration example below. Considering that I hypothetically have an electric DC...

My teacher proved it like this I= ##\frac {E}{R+r}## Where R is external resistance And r is internal resistance E is emf of the cell, Now we can write it like this I= ##\frac {E}{(√R-√r)²+2√R√r}## if R=r then the denominator value will be minimum but i am unable to understand that why this is...

Suppose you have a non-uniformly doped piece of semiconductor (without an applied bias) such that the acceptor dopant concentration Na(x) decreases from left to right (as x increases). In this case, the equilibrium hole distribution p(x) will not be uniform since then there would be a net drift...

The magnetic energy of a current carrying spring, with ##N## turns, length ##x## and cross sectional area ##A##, is $$E_m = \frac{\mu_0 N^2 I^2 A}{2x}$$The (negated) spatial derivative of this yields a quantity with dimensions of force,$$F = - \frac{dE_m}{dx} = \frac{\mu_0 N^2 I^2 A}{2x^2}$$How...

Okay, so according to the transformer equation, VpIp = VsIs In this question, I know I have to calculate Ip. I think given, Vp = 9V, Vs = 120 V Now I don't know what to use in the value of Is. Please help! The answer is 2.32 A.

So the magnetic field induced at the center of a current-carrying loop is given by: B = μ0 i /2r where r is the radius of the loop In the case of a semi-circular loop, this becomes B = μ0 i /4r In the question, i = 2A, r1 = 1m and r2 = 2m So, field induced at the center of first semicircular...

I've been researching dielectric breakdown for a while and came across this interesting experiment: https://tore.tuhh.de/bitstream/11420/1160/1/Size_dependence_of_the_dielectric_breakdown_strength_from_nano_to_millimeter_scale_TUB_Doc_version.pdf 0.3mm of BaTiO3 was placed between two...

Yup, it's mutated to be more contagious and has a higher viral load in patients, but does NOT change the severity of symptoms. It is a mutation that was noted back in Feb., 2020 of the original version from China, it has spread worldwide. 52 page research article in Cell ...

Guys,I need to calculate the flux and current of neutron by MCNP.So what's the difference between them ,and How to calculate them? Any ideas?

How can I' be the formula above? Is there any formula to get this same

I am new to this forum, and this is my first post. Please bear with me if my query has any inaccuracies. In the attached figure, a coil is wrapped around the central arm of a flat H-shaped thin metallic plate (such as iron). DC current flows through the coil and magnetizes the arm. At the...

According to the circuit in the figure; Can you calculate the values of the currents I1, I2, and I3. Can you send me a detailed solution to understand?

In the given question they have not provided the dimensions of the coil so I assumed it to be very close to the wire and having negligible dimensions compared to the wire . Then EMF induced in the coil due to the current in the wire comes out as M*a . Which when divided by resistance gives...

I've been thinking about this but now especially with regards to Covid-19 there are a lot of theories out there starting from absolute fringe and lunacy to somewhat scientific and even ones with sources to academia. For starters not to get too long my question is, What is our current known...

I've learned that moving charges produce magnetic fields which in turn affect other charges in motion. After seeing explanations that point to special relativity, I am kind of confused. Can **ALL** magnetic fields be accounted as some kind of electric field from a particular reference frame...

I am considering switching to a math major with a track in actuarial science (curriculum here https://catalog.louisville.edu/undergraduate/majors/mathematics-bs/#trackrequirementstext), with a minor in computer science (since that will only take me 2-3 more classes). I was wondering, given the...

I thought there was a tiny metal burr on the corner of the lappie, and I kept scraping my forearm across it. Then I thought I had a tiny metal shaving in my skin that I kept brushing on the corner as I typed. Turns out, that little pinprick I'm feeling is electric current. I can only feel it on...

Here, the correct options are A,D. Solution: I got A as answer as ∫ B.dl=µI. But, the answer to the question says that it is a solenoid and therefore Bx=0 for point P. Here I'm a bit confused. I know this system resembles a solenoid in some ways, then By must have some finite value, but...

For an ideal battery (r = 0 Ω), closing the switch in (Figure 1)does not affect the brightness of bulb A. In practice, bulb A dims just a little when the switch closes. To see why, assume that the 1.50 V battery has an internal resistance r = 0.30 Ω and that the resistance of a glowing bulb is R...

(.174A-.181A)/.181A=-3.86% but it says it wrong, and I did (.181A-.174A)/.174A =4.02% but this was wrong too. I've tried 3.87%,3.86%,-3.87%,-3.67%,4.02%, and -4.02% but all were wrong. I'm really not sure what to do here.

Now that currents don't flow past the interior of capacitors at any time (charging/discharging etc), currents should be functions of a spatial coordinate, i(x), in that i(x) is non zero in wires and 0 in capacitors. But in circuits usually currents are assumed constant in the same branch. What...

Summary:: Not sure if my solution to a magnetostatics problem is correct [Mentor Note -- thread moved from the technical forums, so no Homework Template is shown] I was trying to solve problem 2 from...

I have to estimate the electric dipole moment of an NV center in units of Am. I know that for a regular electric dipole moment it can be estimated using p=ed. With e=1.6*10^-19 and d=0.1 nm (interatomic distance), this however is in units Cm. I don't know how to go to Am

In a power transformer, the variation of the current in one circuit induces a current in the other. This cause-effect relationship is two ways. If circuit A affects circuit B, then B circuit will affect A circuit; this is the cause of the concept of mutual inductance. However, it's not necessary...

Why is electric current not a vector while electric current density is a vector? What's the intrinsic difference between the two through that surface integral?

After computind dirac 1D equation time dependant for a free particle particle I get 2 matrixs. From both,them I extract: 1) the probablity matrix P =ps1 * ps1 + psi2 *psi2 2) the current matrix J = np.conj(psi1)*psi2+np.conj(psi2)*psi1 I think that current is related to electricity, and...

Hello. I have completed the following question. My answer: i) Circuit Impedance Reactance = XL = 2 x pi x F x L = 2 x pi x 50 x 0.15 = 47.12 Ohms Reactance of Capacitor = XC = 1/2 x pi x F x C...

I am looking at the module HLK-5M05, which is a ##5\ V, \ 5\ W## AC-DC power supply module. The advantage of this module is that, it does the stepping down and rectification within itself, and is a switching source, so fluctuations in the voltage grid won't affect the output (at least that's...

Hello, let's imagine a generator as shown in image. I just don't understand alternative current. -\epsilon shouldn't be always positive? Otherwise, how can it provide anything? Thanks

A while back I designed a fairly expensive 3-layer PCB (gold plated RF laminate, not cheap). Unfortunately, we have now discovered that I've accidentally put a stiching via, i.e. a vias for connecting top and internal ground planes in the centre of an important RF line which is now permanently...

About this figure, the current in the opposite wires are parallel (and not anti-parallel). So, for instance for the first option the torque is zero; but I wanted to know what is the magnetic moment of this loop. Since I rely only on formula I've have no idea how to compute for this one.

I have attached my solution to this problem but I think I got the wrong answer.

I have written a finite difference program to solve 1D time-independent Schrodinger equation. It seems to work correctly for harmonic oscillator, particle in a box, etc. But I can't figure out how to calculate the probability current density. It should be constant, but what is it? The program...

Can anyone please tell me why the torque on a circular current loop can be calculated by the equation below? In other words, what is the intuition for the formula? Thank you. (I modified my question to a particular case) $$ \vec{\tau} = I \vec{A} \times \vec{B} $$

Hello, in this problem I'm supposed to calculate de magnetic field due to a bent wire at any point of the x-axis after the bending of the wires. It is obvious that the part of the wire that is parallel to the x-axis makes no contribution to the field so we can focus on the other part of the...

It's ABCD question with answers attached. Problem is that, I don't think that neither of those are correct. From KVL the equation seems to be i = (E2-E1)/(2r1+2r2 + R). I've attached images of the circuit, answers, and my solution. Can someone please point me if I am wrong, and if yes, where's...

i have seen several videos of thyristors but they never really explain the fundamentals they just say that cause there is a current flowing in there it keeps being on but why does a transistor then turn off when you remove gate voltage

Let's say we have a circuit, and in that circuit there's a resistor, and there's a wire that goes around it so that the current can flow freely without getting to the resistor. my question is this: how does the current "knows" to flow towards the around the resistor? how does it know not to get...