- #1

CraigH

- 222

- 1

[itex]Work (J) =\int Force(N) .dx(m)[/itex]

I understand this one, work done = force * distance moved in direction due force, but the force can change in magnitude or direction so less/more component of the force is in the direction of movement, so in this case the area under the graph of force vs distance is the work done.

[itex] Force(N) = \int GPE(J) *\frac{-1}{r(m)} .dr'(m)[/itex]

I do not understand this one at all. I;ve never even seen dr' before.

source of equation: http://hyperphysics.phy-astr.gsu.edu/hbase/gpot.html#gpi

And then there are maxwells equations, which make absolutely no sense to me what so ever

[itex]Charge (C) = \epsilon_{0} \oint \stackrel{\rightarrow}{Electric Field Strength}(NC^{-1} or Vm^{-1}) .d \stackrel{\rightarrow}{A}(m^{2})[/itex]

I study electrical engineering, not physics, so when this was taught in our electromagnetism lectures it was the first time I had seen a "closed loop integral", and I still don't understand how this is different from a normal integral. Also what do the arrows mean?

Is this basically saying that the charge that an object has is proportional to the electric field strength at the surface of the object, multiplied by the surface area of the object?

And the reason its an integral and not just a multiplication is that the electric field strength can be different at different places on the surface area of the object?

I have the same problem with the second of maxwell's equations.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/maxeq.html (it takes a while to write them out so i will just reference this list)

The 3rd equation looks similar to what I learned in A level Physics, that the emf induced in a conductor is proportional to the rate of change of flux, where flux is the magnetic field inside a conductor.

What is wrong with this? I can see why a differential is needed to describe the rate of change of flux, but why is an integral needed?

The 4th looks completely new to me, I do not know what this is trying to explain. I don't think we have ever covered this in our lectures, maybe this one isn't as important to electrical engineers.

Also, quick extra question, can any of these be used to derive the electric field strength for a radial field.

[itex]E = \frac{1}{4\pi\epsilon} * \frac{1}{r^{2}} * Q [/itex]

Thanks!

I understand this one, work done = force * distance moved in direction due force, but the force can change in magnitude or direction so less/more component of the force is in the direction of movement, so in this case the area under the graph of force vs distance is the work done.

[itex] Force(N) = \int GPE(J) *\frac{-1}{r(m)} .dr'(m)[/itex]

I do not understand this one at all. I;ve never even seen dr' before.

source of equation: http://hyperphysics.phy-astr.gsu.edu/hbase/gpot.html#gpi

And then there are maxwells equations, which make absolutely no sense to me what so ever

[itex]Charge (C) = \epsilon_{0} \oint \stackrel{\rightarrow}{Electric Field Strength}(NC^{-1} or Vm^{-1}) .d \stackrel{\rightarrow}{A}(m^{2})[/itex]

I study electrical engineering, not physics, so when this was taught in our electromagnetism lectures it was the first time I had seen a "closed loop integral", and I still don't understand how this is different from a normal integral. Also what do the arrows mean?

Is this basically saying that the charge that an object has is proportional to the electric field strength at the surface of the object, multiplied by the surface area of the object?

And the reason its an integral and not just a multiplication is that the electric field strength can be different at different places on the surface area of the object?

I have the same problem with the second of maxwell's equations.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/maxeq.html (it takes a while to write them out so i will just reference this list)

The 3rd equation looks similar to what I learned in A level Physics, that the emf induced in a conductor is proportional to the rate of change of flux, where flux is the magnetic field inside a conductor.

What is wrong with this? I can see why a differential is needed to describe the rate of change of flux, but why is an integral needed?

The 4th looks completely new to me, I do not know what this is trying to explain. I don't think we have ever covered this in our lectures, maybe this one isn't as important to electrical engineers.

Also, quick extra question, can any of these be used to derive the electric field strength for a radial field.

[itex]E = \frac{1}{4\pi\epsilon} * \frac{1}{r^{2}} * Q [/itex]

Thanks!

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