# Search Results

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The classical theory of electric and magnetic fields, both in the static and dynamic case. Also covers general questions about magnets, electric attraction/repulsion etc. Distinct from electrical-engineering.

### electromagnetic waves dependence on frame

In the frame of the particle you just see a constant electric field. From outside this field must change as the particle moves by. Just have a look at this.
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### Electric and Magnetic Field Intensity Analogy

I agree with Lucas Francisco that $H$ is an auxiliary field, but in vacuum one could, e.g., write $$\frac {1}{ 2} \mu_0 H^2,$$ which, for symmetry reasons, looks much better with respect to the elect …
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### Magnetic field of radially emitted alpha particles by a sphere of polonium

The Maxwell way First I assume that the current is homogeneous. In that case the important point to realise is that if current goes away, the sphere becomes charged. If the total current going away i …
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### What determines the magnitude of force of an electromagnet?

As @Uncle-Al said, it depends on shape distance etc. I remember, however, a standard exam question. Assume you have the electromagnet with area $A$ and you want to lift an object that can be magnetize …
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### Cylinder , charge on surface, why is B inside zero?

Just for picturing it...meaning this is not exact: If you are not in the middle, where it is clear, but close to one side you may see it like this: the length over which you see a wire approximately s …
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1 vote
Accepted

### Why is a paramagnetic material attracted into a magnetic field?

I think there is some confusion here. The actual field direction does not play a role for diamagnetic or paramagnetic behavior. What is important is the field strength. What is actually ment by Griffi …
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### energy of eddy current with increasing frequency

In detail eddy currents are very complicated and a 100% answer might not be possible. First of all, it should be clear that the efficiency will not be greater than 100%. The Eddy current is taking en …
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### Shooting a bullet into an MRI

New Version (as I had my doubts on the orders of magnetude...and it turned out that I made a mistake) To simplify things I assume: velocity $v=1000\; \mathrm m /\mathrm s$ perfectly conducting bull …
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### intuitive explanation of $E \times B$ drift with constant and perpendicular $E$ and $B$

For intuition I would like to simplify the continuous circular motion piecewise into four sides of a square: the electric field accelerates the particle in $y$-direction to velocity $v_1$ the magnet …
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A thin wall tube can have a significant effect on coil performance. Unfortunately, for hollow core cylinders analytical solutions only exits for $\lim \mu_\mathrm{r} \rightarrow 1$ or better say $\lim … • 1,580 1 vote Accepted ### How does mu-metal affect magnetic fields? The thicker the mu-metal the more the flux will return inside your horse-shoe construction. The inner field will increase for the following reason: you may think of this in terms of magnetic charge. F … • 1,580 2 votes Accepted ### Currents in circuits Switching on and thinking in the$\mathrm{d}/\mathrm{d}t$properties of$C$and$L$means that the resistance of an inductance is basically infinity and that of a capacitance is zero. For long times t … • 1,580 6 votes Accepted ### Magnetic levitation frog example Yes, the frog will be repelled from the field if the field is non-uniform. Its magnetic moment is given through the susceptibility of Water$\vec \mu = V \chi \vec H$and$\chi_\mathrm{water}\approx …
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Your formulae are correct. The movements are comletely independent like in an inclined trajactory of a thrown ball where $v_x$ and $v_y$ are independent: one is constant ,the other affected by acceler …
If you bring two magnets together in such a way that they repel each other, you store potential energy $E_\mathrm{pot}$ . This is correct. The force will be the according derivative \$F=-\mathrm{d} E_\ …