### Logging In

You will need to log in so that we can save the problems you start. Whenever you select a problem for the first time, we generate a new set of parameters. These will be saved under your user name so that you will get the same problem when you log in again. When you submit your answers, we will tell you whether they were correct or not. You can keep trying until you get it right. Some of these practice problems are easy enough that you can work them while you are on line and submit the answers. Others may require more time and effort. On these, you may want to print the problem statement before you leave the site, work the problem off-line, then log-in again and submit your answers for checking. Then you can choose an entirely new problem to work. Are we having fun, yet?

### What? You don't have an account?

If you are not a registered student in a participating course nor an instructor, you will not be able to log in. However, You can still practice on the problems. Go to Guest Login. Then choose one of the guest identities; i.e., Guest_01, Guest_02, ... etc. then pick a course or select "all probs" to see everything. If you are a student enrolled in one of the courses, be aware that problems solved as a guest will not accrue credit for your homework. This is for extra practice.

### Entering Very Large or Very Small Numbers

Most of the problems on this homework site have answers that are dimensioned to be between 1 and 1000. I.e.,
if an answer were 50 milliamps, we will append "mA" as the units to the right of the input box and you would
simply enter the number *50* into the answer box. However, some of the answers are very
large or very small numbers. In these cases, you will need to use "scientific notation" in order to get
your answer accepted. For example, if you have calculated that the number of electrons passing a point
in a circuit to be 40 × 10^{23}, you would enter *40e23* where *40* is the mantissa and the
exponent is *23*. If you calculated a charge to be 75 × 10^{-15} coulombs, you would enter
*75e-15* in the answer box. The letter *e* is just the way we tell the server that we are using scientific notation.