Q: Induced EMF (1 Viewer)

[Studentleader]

Can't seem to get this one:

A record collector plays an Elvis LP, made of platinium, on a turntable that rotates at 33 RPM. Assume that the direction of the Earth's magnetic field is allways perpendiculr tothe plane of the record, and has a uniform strength of 5.0x10^-5 T. The radius of the record is 26 cm.

What EMF would be induced between the center of the record and the rim?

- Answer is 5.8x10^-6 V

My working so far

EMF = L x B x V

= (0.26) x (5.0x10^-5) x (0.52 x pi x 33)
= 7.01 x 10^-4 V

V = l x pi x RPM

 

[Forbidden.]

B = 5.0x10^-5 T (Given magnetic flux density)
A = πr² (The record's shape is a circle)
r = 0.26 (Converting to S.I. units i.e. 26 cm = 0.26 m)
t = 60 (The record has turned one whole minute or 60 seconds)
n = 33 (The record rotates 33 times)

V_induced = - nΔΦ/Δt
But ΔΦ = Δ(BA) = ΔB(πr²)
V_induced = - nΔ(Bπr²)/Δt
V_induced = - (33)[(5.0x10^-5)(π)(0.26)²/(60 - 0)
V_induced = - 5.84x10^-6 V

If the formatting seems a little cluttered to you, view the working out here:
http://img156.imageshack.us/img156/1639/voltagesn3.gif

 

[Studentleader]

So... i like owe you sex now right?

thanks

Edit: what program did you make that GIF in?

I use sciwriter exept it seems to just crashon my vista laptop :S

 

[Forbidden.]

So... i like owe you sex now right?

thanks

Edit: what program did you make that GIF in?

I use sciwriter exept it seems to just crashon my vista laptop :S

Nah I don't take dick buddy.
I use MathCast Equation Editor but it can't export equation(s) as pictures.
So I screenshot it then convert the BMP screenshot to a GIF using IrfanView then upload it.