Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community for help and clear up your study doubts
Discover the best universities in your country according to Docsity users
Free resources
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
The weekly assignments and key concepts for physics 122 students, focusing on electromotive force (emf), which is actually voltage, and faraday's law. Students are required to complete homework problems, read assigned chapters, and attend class. The document also discusses the concept of generating emf through magnetic fields and the use of motors as generators. Lenz' law and mutual induction are also introduced.
Typology: Assignments
1 / 15
This page cannot be seen from the preview
Don't miss anything!
HW 8: Chapter 27, problems 16, 19, 22, 32, 50, and 71. Due date moved to Friday. Mastering Physics: due tomorrow by midnight. Reading: have chapter 27 finished for Wed. Congratulations: on making it to your 8 am class after 49ers (unless you didn't, and you're reading this on the web later!).
The key to generalizing EMF (ElectroMotive Force, which is actually VOLTAGE rather than a force) when magnetic fields are present: integrate the Electro-Magnetic Force (which IS a force) per charge, F / q , over distance:
This also generates an EMF! But if the magnetic field were uniform, it wouldn't.
Clickers: It seems as though we could just allow the loop to keep moving, and we'll keep getting power from it! Can this solve some of our energy problems?
Every motor can also be used as a generator!
This version of Faraday's Law is almost always true! There are some EMF s which don't have changing magnetic flux, however. As with the previous EMF definition, the convention is that positive EMF is “downhill”: in the direction of the current. There is yet another right-hand-rule for this: if your right-hand thumb points along the convention of positive flux (on the right of the equation), then your right hand fingers curl in the positive EMF convention (on the left side of the equation).
Mutual Induction: A change in current in one circuit generates an EMF in the other. This principle is behind the transformer, and one form of the wireless transmission of power.
Lenz' Law: Induced EMF always acts in a direction to oppose the change in magnetic flux. After a bit of practice, Lenz' Law is MUCH easier to use than the complicated right-hand-rule version given earlier! You are advised to become a “black belt” master user of Lenz' Law.
Clickers: If the magnetic field in the previous slide were DECREASING instead, which direction would the current flow?
Faraday's Law in one final form, which is valid for any STATIONARY loop in space: This says that whenever a magnetic field changes with time, electric fields are generated! The electric fields are there in space no matter what (whether a conductor is there to make a current flow, or not).
