# Electromagnetics Help

1. Dec 9, 2003

### Wxpunk

Hello! I'm looking for some hints or tips on a few problems in Electromagnetics. Everytime I approach a problem, I get frustrated and end up turning in crap. Then I find out the problems weren't so hard had I approached them differently. Anyhow, can anyone here help with this level of physics?

Oh, please don't be insulted by my asking if anyone can help from this forum. Maybe I should ask if anyone will help. If you guys are willing to help, I'll post a few problems.

Thanks!
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Wxpunk

Last edited: Dec 9, 2003
2. Dec 9, 2003

### gnome

Why don't you post a question & YOUR attempt at solving it, & maybe someone can show you the light.

3. Dec 10, 2003

### himanshu121

Yes we will help if you post your Que along with Try, but we want to see your attempt first even your thought process will help us to show u way

4. Dec 10, 2003

### Wxpunk

Okay, here's the problem:

Two infinitely long wires carrying currents $$I_1$$ and $$I_2$$
cross (without electrical contact) at the origin. A small rectangular loop is
placed next to the wires, as shown below

http://home.insightbb.com/~wxpunk/phys2.jpg [Broken]

1. Obtain expressions for the B field at an arbitrary point inside the
rectangular loop due to the two infinite wires. Hence write down an
expression for the net B field at an arbitrary point inside the
rectangle.

2. Obtain the magnetic flux ($$/Phi _B$$) through the small rectangular
loop (in terms of $$I_1$$, $$I_2$$, a, d, and b).

3. If $$I_1 = I_0 cos /omega {t}$$ and $$I_2 = sin /omega t$$ determine the magnitude of the induced emf in the
rectangular loop.

4. On the same graph, sketch the time dependence of the induced emf,
$$I_1$$ and $$I_2$$.

5. Suppose $$I_1$$ and $$I_2$$ are constant, but the rectangular
loop is moved away from the infinite wires at a constant velocity, v.
Obtain an expression for the induced emf as a function of the angle of the
constant velocity with respect to the x axis.

6. What direction should the loop be moved in order to produce the maximum
induced emf in the loop?

I'm still working on the first part. Like I said, I get frustrated and don't
know where to begin. This is the direction I'm going though...

http://home.insightbb.com/~wxpunk/phys1.jpg [Broken]

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Wxpunk

Last edited by a moderator: May 1, 2017
5. Dec 10, 2003

### BigRedDot

The magnetic field from an infinite wire circles the wire (with a direction given by the right hand rule) and has a magnitude that is inversely proportional to the distance from the wire:
$$B = \frac{\mu_0 I}{2\pi s}$$
You have two infinite wires; why don't you try superposing their solutions first.

6. Dec 11, 2003

### himanshu121

I hope you have done the First problem with the above formulae

For the second part calculate the flux due to I1&I2 Due to I1 it will be into the plane and due to I2 it will be outwards.

You can consider the loop to be divided into small parts then aply the formula for flux

$$\phi_1= \int_d^{a+d} \frac{\mu_0{I_1}}{2\pi x}dx$$

If you have grasped it then we will move to next portion

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Last edited: Dec 11, 2003