act07ans - _ANSWERS_ PHYS-1200 PHYSICS II Class 7 Activity:...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
___________ ANSWERS __________________ PHYS-1200 PHYSICS II SPRING 2006 Class 7 Activity: Faraday’s Law The relation between an induced electromotive force (emf) and a changing magnetic field is given by Faraday’s Law. Today, you will use Faraday’s Law, a coil of wire, and a computer to measure the strength of a magnetic field. Let us examine Faraday’s Law to see how it can be used to measure a magnetic field. If a coil of wire, consisting of N turns, experiences a changing magnetic field, the magnetic flux through it will change. That will induce an electromotive force, E , as described by Faraday’s Law: E E = - = - N d dt dt N d B B Φ Φ , so If both sides of the equation on the right are integrated, the result is, ( 29 E dt N d N t B B f Bi B i B f 0 = - = - - Φ Φ Φ Φ Φ That is, the integral of E over time is equal to the change in flux through the coil times the number of turns in the coil. Now imagine that the coil is initially in a strong magnetic field, and ends up in a magnetic field of zero. Then the equation becomes, ( 29 i B i B t N N dt Φ = Φ - - = 0 0 E . However, the flux through the coil, when it is in the magnetic field, is equal to the average value of the magnetic field in the coil, B av , times the area of the coil, A . Since the coil is circular, this can be written as, 2 r B A B av av i B π = = Φ . Then the equation for the integral becomes, 2 0 r NB dt av t = E . Finally, the equation can be solved for B av to give, B dt N r av t = E 0 2 With the help of LoggerPro, t dt 0 E can be measured, and B av can be calculated. 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
___________ ANSWERS __________________ You will need LoggerPro in today’s activity. Make sure that one person in each group has a computer hooked up to a LabPro and running LoggerPro. Connect a LabPro to your computer through a USB port. There are links to the LoggerPro file that you will need for this experiment at the Physics II web site under “Activities” If you are running LoggerPro 2.2 do the following: Select the link “Faraday for 2.2”. Download the file “Faraday2.MBL” to your desktop. Double click on the icon to start the program. If everything is working correctly, your screen will show a “Collect” button above a graph of potential vs. time. If you are running LoggerPro 3.2 do the following: Select the link “Faraday for 3.2”. Download the file “Faraday3.xmbl” to your desktop.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/07/2008 for the course PHYS 1200 taught by Professor Stoler during the Spring '06 term at Rensselaer Polytechnic Institute.

Page1 / 7

act07ans - _ANSWERS_ PHYS-1200 PHYSICS II Class 7 Activity:...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online