# Homework Help: Inductance problem

1. Sep 11, 2008

### fredrick08

inductance, flux, capacitance
1. The problem statement, all variables and given/known data
The magnetic field at one place on the earth’s surface is 55 μT in strength and tilted 60°
down from horizontal. A 200-turn coil having a diameter of 4.0 cm and a resistance of 2.0 Ω
is connected to a 1.0 μF capacitor rather than to a current meter. The coil is held in a
horizontal plane and the capacitor is discharged. The coil is then quickly rotated 180° so that
the side that had been facing up is now facing down. Afterward, what is the voltage across
the capacitor? [Hint: use I=dq/dt

2. Relevant equations
LaTeX Code: \\Phi =ABcosLaTeX Code: \\theta
Vc=Q/C
Vl=-L(di/dt)
Vc=-Vl
I=LaTeX Code: \\Phi /L
LaTeX Code: \\Phi =NLaTeX Code: \\Phi per coil

3. The attempt at a solution
ok wat i did was find flux per coil=LaTeX Code: \\pi r2BcosLaTeX Code: \\theta =3.45x10-8
then flux=3.45x10-8*200=6.9x10-6=L(di/dt)=Q/C....
but that cant be right coz i know the answer is 12V... can someone please help me, ive been on this for 4 or hours and its 3am almost... due in tomoz... plz someone help... 1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Sep 11, 2008

### fredrick08

any ideas??

3. Sep 11, 2008

### fredrick08

plz im getting disparate here... well emf=|d$$\Phi$$/dt|=L*di/dt=6.91x10-6... does not sound right at all!!!
emf=IR=>I=emf/R=... oh id dunno plz!!

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