1
vote
1answer
39 views

Calculating the magnetic field due to a rotating ring using Biot–Savart law

I wish to calculate the magnetic field due to a charged ring rotating about an axis perpendicular to the plane of the ring and passing through a point on its circumference $(P)$. I arrive at something ...
0
votes
1answer
100 views

Post Problem Analysis - Rod in a cylindrical time varying magnetic field?

A metal rod of length $l$ is placed (as shown in figure) in a cylindrical time varying magnetic field. Find the potential difference across it. My answer: As electric fields as forming circles ...
1
vote
0answers
51 views

calculate force between two magnets [closed]

I have used a couple of online calculators to estimate the attractive force between two cylindrical bar magnets. Using d=1"; t=1"; x=0.1"; Neo35 (Br=12,300 Gauss): source 1 gives 63.5 lbf source 2 ...
0
votes
0answers
32 views

Finite rod aligned with a time varying magnetic field

A finite length rod is aligned parallel with a magnetic field that has a changing magnitude (let's say a sinusoidal change), given the conductivity and permeability of the rod and assume a large ...
0
votes
1answer
24 views

Determine stationary angular velocity of wheel with circuit in magnetic field

I have a wheel (free to spin around the $z-$axis) with four spokes that is connected by sliding contacts to a circuit with $U_0 = 0,72V$. Also, there is a B-Field parallel to the $z-$axis For the ...
0
votes
0answers
22 views

Torque per unit length on infinite rotating charged cylinder

For homework I have the following question, but I am stuck on finding the torque on the cylinder. An infinite cylinder of radius $R$ carries a uniform surface charge $\sigma$. We start rotating the ...
0
votes
0answers
59 views

How do I use the direction of a cross product?

The question is: An electron is projected at a speed of $3.70×10^6\text{ m/s}$ in the $u=\frac{(i+j+k)}{\sqrt3}$ direction into a uniform magnetic field $\vec {B} = 6.43 i + 3.43 j −8.29 k$. ...
0
votes
2answers
90 views

Work done by magnetic field on magnetic dipole

In the above slide, it reads that $W=\int\mu B sin(\theta)d\theta=\mu B cos(\theta)$. But, I thought that $\int\mu B sin(\theta)d\theta=-\mu B cos(\theta)$ by some calculus calculation. Can ...
1
vote
0answers
23 views

Sphere in homogenou magnetic field

I have to find out the magnetic dipole moment of sphere in homogenou magnetic field in the limit $\mu_r\rightarrow+\infty$. I don't know what does the condition $\mu_r\rightarrow+\infty$ mean. Does ...
2
votes
2answers
353 views

Is magnetic force non-conservative? [duplicate]

If magnetic field is conservative, then why not the magnetic force? My professor thinks it is non conservative but he couldn't explain to me why?
1
vote
0answers
44 views

Freely Falling Bar in a Magnetic Field

I have a horizontal bar on vertical rails and we can consider that does not exist any friction. Perpendicular to the plane of the rails it exists a magnetic field $B$. I am asked to find the ...
0
votes
1answer
45 views

Current in Magnetic fields

I have two magnetic fields question (high school level) which require clear answers... When a current carrying conductor, such as a copper wire, is placed in a magnetic field it will experience a ...
1
vote
1answer
270 views

Moving in a heart!

You can find the symbol of love, the heart, by looking at the motion of a charged particle that's emitted from a hot wire in a specific electromagnetic field. The electric field is directed radially ...
0
votes
1answer
165 views

Magnetic field inside finite solenoid

In my book they don't really derive the equation of the magnetic field inside of a finite solenoid. They just give me equation 1 and image and the end result, equation 2. ...
2
votes
3answers
440 views

Why doesn't Lenz's law predict the behavior of a rod on springs in a magnetic field?

This comes from one of the free response questions from the AP Physics B 2014 exam. 5. (15 points) A conducting rod of mass $m$ and length $L$ hangs at rest from two identical conducting ...
-3
votes
1answer
70 views

Magnitude and Direction of Magnetic Field Homework Question [closed]

A $150~\text{V}$ battery is connected across two parallel metal plates of area $28.5~\text{cm}^2$ and separation $0.00820~\text{m}$. A beam of alpha particles (charge $+2e$, mass $6.64 \times ...
1
vote
1answer
46 views

Heat generated on thin disc plate in magnetic field [closed]

There are the eddy currents in thin circular copper plate thickness h and radius a, in a harmonic magnetic field which is perpendicular to plate and the effect of auto-induction is negligible. Now we ...
0
votes
1answer
53 views

Earth's magnetic field

I'm dealing with a problem here. Today my professor asked us a question : How should a metallic wire move in Earth's magnetic field such that she gets maximum potential difference in it's ends: a) ...
0
votes
0answers
20 views

Flux, intensity, etc in ferromagnetic core by integral

Cheng, Field and Wave Electromagnetics (newest ed.), ex 6-10, page 252 Some of the examples in this book are kind of sloppily described. Having trouble with this one. We have a toroidal core with ...
1
vote
1answer
85 views

Equation for magnetic field due to a current in straight wire [closed]

How can I derive the expression for the magnetic field due to a long straight current carrying wire using the Biot-Savart law? The final expression should be: ...
0
votes
1answer
97 views

Magnetic Shielding?

Can magnetic fields be "blocked"? For example, in the game, TitanFall, a robot stop bullets with ( presumably ) a magnetic shield. I wish to calculate the magnetic force required to stop a bullet ...
0
votes
1answer
60 views

How does this particle behave in the magnetic field?

I have the above question and I have though about it every way and can't seem to find out. So what I have concluded (ignore the answers on the img) Is that the force is on the z axis because the ...
0
votes
1answer
404 views

Determining $y$ coordinate of charged particle motion [closed]

I've tried several different ways, with a tutor, and with other colleagues. One of my colleagues has even gone to the professor with whom he worked out an equation for the component, and it was later ...
0
votes
0answers
52 views

Graph of Lorentz force in function of angle between v and B-field?

I need to draw a graph of the magnitude of the Lorentz force in function of the angle between the velocity and B. Am i right in supposing this will be a sine wave?
0
votes
1answer
98 views

Calculating the magnetic field from rectangular conductor?

I want to apply the Biot-Savart law to calculate the magnetic field at a point created by current flowing through a square/rectangular conductor. More specifically, a trace on a printed circuit board. ...
0
votes
0answers
90 views

Calculating repulsion due to eddy currents?

I have a conductive particle moving at a known speed through changing magnetic field (Permanent magnets attached to a rotating drum alternating north/south). These particles will have induced eddy ...
2
votes
1answer
83 views

$\hat{\imath}$ component of force exerted on an electron by a magnetic field?

The magnetic field over a certain range is given by $\vec{B} = B_x\hat{\imath} + B_y\hat{\jmath}$, where $B_x= 4\: \mathrm{T}$ and $B_y= 2\: \mathrm{T}$. An electron moves into the field with a ...
0
votes
1answer
39 views

Want to achieve maximum magnetic force & find out the max point [closed]

Hi Sir/ Madam Want to achieve maximum magnetic force & find out the max point for this setting, want to know is the strongest magnetic force must in the 'dot' area ( middle poin of setting ) ...
-5
votes
1answer
492 views

Tesla to Newtons [closed]

Is it possible to convert Tesla to Newtons of force? Or magnetization force H:(A/m) to newtons?
1
vote
0answers
350 views

Current flowing through a square loop - Magnetic Field [closed]

A square conducting loop of wire of side $2a$ carries a uniform current I. Calculate the magnetic field at the centre of square due to the current in the loop.
1
vote
0answers
40 views

Lorentzforce and righthand rule [closed]

Figure 1: A spool is hung on a spring. A part of the coil hangs in front of a homogeneous magnetic field. The coil is incorporated in an electrical circuit. See Figure 1. the coil ...
0
votes
2answers
636 views

Ampere's law on a long wire with varying current density [closed]

On a question from my book: A long straight wire with a circular cross section of radius $R$ carries a current $I$. Assume the current density is not constant over the cross section of the wire, ...
0
votes
1answer
136 views

determining Induced emf/current through v x B . l

I am working on a question from my book. I am wondering how they conclude emf is negative in this case. looking at $$ \mathcal{E} = \vec{v} \times \vec{B} \cdot \vec{dl}$$ If there's some implied ...
1
vote
1answer
130 views

Flux increase due to velocity?

I have a book question I'm trying to understand: The first bit is easy enough. The second part I was confused so I checked the solution: B is into the page. The flux increases as the bar moves ...
1
vote
1answer
147 views

Question about superconductivity

A long cylinder of radius $R$ is made from two different material. Its radius $r<r_0$ $(r_0<R)$ part is a material with superconducting transition temperature $T_1$, and its $r_0<r<R$ ...
2
votes
1answer
242 views

Lorentz Force Law and cycloid motion

The question I have is from Intro to Electrodynamics by Griffiths (Page 206, Example 5.2) http://imgur.com/a/sfBlt When using the initial conditions $y(0) = z(0) = 0$, I get: $y(0) = 0$ implies ...
1
vote
3answers
2k views

Magnitude of magnetic field at the center of circular wire

I'm preparing for an exam by solving the sample questions , here is the one I'm having difficulty with : Following is the given circuit. Which contains two resistance $R_1$ and $R_2$ in form of ...
0
votes
1answer
63 views

Energy spent by motor in a period

Consider a single coil that is turning in a constant and uniform magnetic field thanks to a motor. The normal to the coil is given by: $${\bf u}(t)=\sin (\omega t){\bf u_x}+\cos(\omega t){\bf u_z}$$ ...
0
votes
1answer
403 views

Pressure experienced due to magnetic force?

A current $I$ flows in a long thin walled cylinder(parallel to the axis) of radius $R$. What pressure do the walls experience? This is the 263rd problem in Section III from the book 'Problems In ...
2
votes
2answers
269 views

accelerated charged particles and interaction with magnetic field

In high school we are taught that magnetic field perpendicular to velocity of an charged particle experience perpendicular force that causes it to move in circular path by relation ...
1
vote
1answer
2k views

How to find the direction of the magnetic field for an infinite conducting wire?

We've got two long straight wires carrying current of 5A and placed along x and y axis respectively current flows in direction of positive axes we have to find magnetic field at a) (1 m,1 m) b) (-1 ...
4
votes
0answers
79 views

Quantum Cyclotron Frequency - Why is it off by a factor of 2?

Say you have a magnetic field $\vec{B}=(0,0,B_0)$. Then the Schrodinger Equation Hamiltonian for a spin-2 particle of charge $e$ moving in this field is: $$H = ...
2
votes
0answers
159 views

Current to cancel Earth's magnetic field

I'm making a lab report where I've used a Helmholtz coil and a magnet to find Earth's magnetic field intensity in the area by relating the frequency of oscillation of the magnet when a certain current ...
5
votes
2answers
2k views

Magnetic force doesn't do work and therefore can't change the KE of a particle?

I am having a real hard time understanding the principles behind a question I've come across during test prep. Here is the question: Q: A proton and an electron are traveling in the uniform ...
0
votes
1answer
64 views

Superconducting magnet

This is a somewhat more detailed question related to this one. The problem I want to solve is problem 1 here. What I tried: a) From $V=-L\frac{\mathrm{d} i}{\mathrm{d} t}$, we can integrate and ...
3
votes
0answers
208 views

Finding the terminal velocity of a magnet dropped in a solenoid

We have to find proportionality of the terminal velocity with the factors of the system: Plot: a small dipole(mass $m$) with dipole moment $\mu$ is dropped in a long solenoid (radius $r$, ...
1
vote
1answer
505 views

Superconducting diamagnetic sphere in uniform magnetic field

What is the size of the magnetic dipole moment $\vec m$ of a superconducting diamagnetic sphere $radius=R$ in a uniform magnetic field $\vec B_0$? Since there is no free current, we can solve for ...
2
votes
1answer
167 views

Liquid benzene magnetic susceptibility

In a solid state physics problem, I'm asked to make a rough estimate of the contribution to the diamagnetic susceptibility of the outer electron of each carbon atom. The wavefunction of these ...
1
vote
2answers
188 views

Movement of the particle in a magnetic field

This is the numerical question. A particle having a mass of 0.05 mg carries a charge of $5\times10^{-6}C$. The particle is given an initial horizontal velocity of 5000 m/s, what is the magnitude ...
0
votes
0answers
327 views

Equation of motion of charged particle under effect of magnetic field

A charged particle with specific charge q/m diverges from the origin [to the first quadrant] by angle X with x axis and with velocity v. To bring the particle back to the x axis, a magnetic field B is ...