# Electromagnetic Induction

1. Sep 2, 2004

### islandguy

a) State Faraday’s law of electromagnetic induction.
[ mark
b) A coil of 1000 turns, resistance 23.0 ohms and cross-sectional area of 4.0 cm squared is positioned perpendicular to a magnetic field which is switched off in 0.005 s.
I) What is the average induced e.m.f. if the magnetic flux density of the magnetic field is 5.3 x 10^5 T?

ii) What is the average electrical power generated in the coil if its ends are short circuited?

If its not asking to much, give me answer i need to compare to mine

Thank you for ur kindness

Last edited: Sep 2, 2004
2. Sep 2, 2004

### Tide

Tell us what you got and how you got it! :-)

3. Sep 2, 2004

### humanino

sounds like homework, is it not ?

a) the formula gives the emf (generated voltage = "electro motrice force" is it not ?) $$\epsilon$$ (the minus sign is Lenz's law)
$$\epsilon = - \frac{d\phi}{dt}$$

You can find this anywhere, this is no big deal just giving it to you. Typing "Faraday induction" in google is enough.

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EDIT I first gave the answers to the other questions, then deleted them because of the previous post. Yet, I would also doubt about the huge numbers obtained. This is because of the enormous magnetic field.

Last edited: Sep 2, 2004
4. Sep 2, 2004

### islandguy

shouldnt be the formula: E = -N *(dф)/(dt) ?

ur right about the magnetic fiels it should be to the power of -5, sorry for that mistake

Last edited: Sep 2, 2004
5. Sep 3, 2004

### humanino

Either you define the flux through one coil, and then you get an extra N factor, or you define the flux through the N turns from the begining. But yes, don't forget the N in the formula. Since your coils are perpendicular to the magnetic field, the equation is quite simple.