# Emf max for a guitar string.

1. Oct 31, 2008

### Ithryndil

1. The problem statement, all variables and given/known data
Review problem. A flexible metallic wire with linear density 3.00 multiplied by 10-3 kg/m is stretched between two fixed clamps 64.0 cm apart and held under tension 301 N. A magnet is placed near the wire as shown in Figure P31.25. Assume that the magnet produces a uniform field of 5.00 mT over a 2.00 cm length at the center of the wire and a negligible field elsewhere. The wire is set vibrating at its fundamental (lowest) frequency. The section of the wire in the magnetic field moves with a uniform amplitude of 1.50 cm.

http://www.webassign.net/serpop/p23-18.gif

(b) Find the amplitude of the electromotive force (emfmax) induced between the ends of the wire.

2. Relevant equations

Emf = BA

3. The attempt at a solution

I am not quite sure I am doing the problem correctly. I had the area being 3.00cm X 2.00cm but that's not correct nor do I actually believe the above equation is the correct equation. I assume the equation needs to have a sine or a cosine in it, but we are needing to find Emfmax so that's not too important right? Thanks for the help.

2. Nov 1, 2008

### Redbelly98

Staff Emeritus
Correction to your equation:

$$Emf = \frac{d}{dt} (BA)$$

Since B is constant, the problem comes down to finding dA/dt.