# Questions tagged [electromagnetism]

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.

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### EM-Wave: Calculate magnetic field $H$ from electric field $E$

In an exercise I am supposed to calculate the magnetic field from the electric field for a plane, harmonic wave in vacuum. $$\vec{E} = - E_0 \cdot \sin(\omega t - k z) \cdot \vec{e_y}$$ Using the law ...
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### Magnetic fields and closed loop

It is well known that there don't appear to be magnetic poles. In Maxwell's equations this has the implication $$\nabla \cdot \mathbf{B} = 0$$ and results in the statement "the magnetic field forms ...
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### Magnetic Field Manipulation

For a reference of my level of knowledge, I have taken an undergrad electromagnetism class, and it wasn't pretty but I passed. I have a real interest in this so I don't mind doing more research. If ...
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### Why are there many turns in the primary coil of a step-up electricity transformer?

Since the voltage in a coil is proportional to the number of turns, the ratio of voltages is equal to the ratio of turns. So if you need a big increase in voltage, what stops you from having one turn ...
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### Prerequisites for Griffiths electrodynamics [duplicate]

I want to start reading Griffiths electrodynamics during my holidays. But I am not sure of the math I need to know to start reading and understand the text thoroughly. So any advice would be ...