# Tagged Questions

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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 $\vec {B} = 6.43 i + 3.43 j −8.29 k$. ...
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### 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 ...
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### 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 ...
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### 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?
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### 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 ...
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### 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 ...
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### 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 ...
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### 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. ...
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### 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 ...
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### 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 ...