# Planning Lab to measure how emf varies with an angle

1. Mar 9, 2008

### rock.freak667

A metal disc is placed in a uniform magnetic field of flux density,B,acting through the plane of the disc at and angle,$\theta$.When the dis is rotated an e.m.f. is induced between the centre and the rim of the disc.

http://img158.imageshack.us/my.php?image=scanlc2.jpg

Design an experiment to investigate how the induced e.m.f.,E, depends upon $\theta$

ok, since I am I need to measure E and $\theta$, I need to keep the rest constant.
$\omega$ would be kept constant by using a motor with a constant power output to rotate the disc.

To keep B constant, use a solenoid and the field should be uniform through the centre of it. (Not sure about that)
But I do not know how to go about measuring the angle.$\theta$

2. Mar 10, 2008

### dlgoff

"To keep B constant, use a solenoid and the field should be uniform through the centre of it. (Not sure about that)"

You would need a very large solenoid since you want B to be constant over the whole surface area of the disk. i.e A large pole-face.

"But I do not know how to go about measuring the angle..."

Just tip the magnet at a know fixed angle relative to the disk surface. Your choice.

Last edited: Mar 10, 2008
3. Mar 14, 2008

### rock.freak667

So take a protractor and just move the magnet relative to the protractor?