# Lenz's Law and Motional EMF

1. Mar 31, 2005

### SurrealityCheck

if someone could help me with understanding the basics of Lenz's law and Motional emf i'd really appreciate it. i'm having some trouble applying it to questions that were assigned.

2. Mar 31, 2005

### whozum

If you could ask a question we could work through it with you. Given what you told me all I could tell you is what lenz' law is, but you probably already know that.

3. Mar 31, 2005

### pmb_phy

With Lenz's law there is an emf produced when there is a changing in flux. A motional emf does not need a change of flux to produce an emf.

Pete

4. Mar 31, 2005

### Crosson

Assuming you are in the general physics for majors class, this is how you will be applying lenz's law:

First, lets define flux:

$$\Phi = \vec{B} \cdot \vec{A} = B*A*cos(\theta}$$

B is the field, A is the area (through which the flux passes).

In all of the problems you will be doing, the flux is a function of time. This means that either B or A or the angle between them is a function of time (rarely will more than one of these quantities be a function of time).

All of the problems consist of constructing this function and taking its derivative to get voltage. Please ask specific questions.