# electromagetism Definition and Topics - 252 Discussions

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1. ### I Electrical disturbances

The electromagnetic field can carry waves, some of them are light, others are used in radio broadcast. These oscillatory waves are distinguished by their frequency. The usual pickup that we get from electric currents in the circuits in the walls of the building has a frequency of about 100...
2. ### Force on a charge centered around a rotating magnet

Charge will experience a rotating magnetic field around it. What will be electric field ( If any ) at the centre, generated by rotation of magnet ?
3. ### Proving modified Maxwell action is gauge invariant

I want to show that the action staying the same action after taking ##A^\mu \to A^\mu + \partial ^\mu \chi##, for the first term I suceeded in showing the invariance using the fact ##[\partial ^ \mu , \partial ^\nu]=0## but for the second term I'm getting: ##\epsilon^{\alpha\mu\nu}A_\alpha...
4. ### B Are silicon iron sheets really necessary for a commercial transformer?

Hi, everyone. I just finished studying the principle on which a transformer works. It relies on Faraday's law of induction. And my high school physics book uses the following picture for illustration: Roughly speaking, the...
5. ### Electric field acting on the source charge

I am reading Griffith's textbook on EM. There is a problem asking to find the force acting on the northern hemisphere by the southern hemisphere of a uniformly charged sphere. The solution idea is to find the expression of the E field by Gauss's law and integrate the force over the northern...
6. ### Electromagnetism - movement of a coil in a magnetic field

So my idea was that to reach the equilibrium position, the final moment of force has to be 0 (so in the end the forces will “eliminate” each other). And I found the equation Fm=B*I*l*sinα, which should characterize the force, which affects wire with the current in a magnetic field, and Fleming’s...
7. ### Find maximum current in a coil using oscilloscopes and Faraday's Law?

The experiment consists of a large field coil (connected to a current source) surrounding a coplanar and coaxial small detector coil in the center of the field coil connected to the oscilloscope. 1. Matching Current v. Time Graphs to Oscilloscope Graphs Example of one pair of graphs (I'll...

26. ### Antisymmetry of the electromagnetic field tensor

I am trying to answer exercise 5 but I am not sure I understand what the hint is implying, differentiate with respect to ##p_\alpha## and ##p_\beta##, I have done this but nothing is clicking. Also, what is the relevance of the hint "the constraint ##p^\alpha p_\alpha = m^2c^2## can be ignored...
27. ### The difficulty of learning Electromagnetism vs Classical Mechanics

There was an old thread comparing the difficulty of classical mechanics and electromagnetism. The consensus was that electromagnetism is more difficult, and substantially so according to some. The thread was no longer open for replies, but it got me suspecting that we're comparing apples to...
28. ### I Electric Field Directly Ahead of or Behind a Moving Charge

Since it is stated that ##E'_x = E_x##, I am going to set a special case where ##z' = z = 0##, ##E_x## in (5.10) reduces to, ##E_x = \frac{1}{4 \pi \epsilon_0}\frac{Q}{x^2}## However, ##E'_x## in (5.13) reduces to, ##E'_x = \frac{1}{4 \pi \epsilon_0}\frac{Q}{\gamma^2 x'^2}## There is an...
29. ### Vector potential of current flowing to a point from all directions

I am having problem with part (b) finding the vector potential. More specifically when writing out the volume integral, $$A = \frac{\mu_0}{4\pi r}\frac{dq}{dt}\int_{0}^{2\pi}\int_{0}^{\pi}\int_{0}^{?}\frac{1}{4\pi r'^2} r'^2sin\theta dr'd\theta d\phi$$ How do I integrate ##r'##? The solution...
30. ### Electromagnetism EMF induction calculations

A square conducting loop of side length a is in a non-uniform magnetic field. The loop occupies the first quadrant of the xy plane, i.e. the space between the origin (x, y) = (0,0) and the point (x,y) = (a, a). The magnetic field is in the +z direction. Develop an expression for the magnitude of...