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Random helpful notes for your experiment:

1. Ohmic materials are those with a constant value of the resistance, R, for ALL values of V and I. Non-ohmic materials have a R that varies with V and/or I. Since V = IR, a constant R implies a constant slope (and, hence, a linear graph) for the V/I graph (or, as in the lab manual, a I vs. V graph) whereas a variable R gives a screwy I vs. V graph (see Fig. 1 on p. 24).
2. The difference between average and dynamic resistance:
   • R_average is the Resistance at a single point that is found using Ohm's Law (V=IR).
   • R_dynamic, on the other hand, is found by choosing two points on the graph (one point above and one point below the point you're interested in finding the resistance at; see the sample R_d the manual finds on p. 24) and essentially finding the slope between them (more correctly, the inverse of the slope of the I vs. V graph since the resistance R is the slope of the V vs. I graph).
   • Confused? Don't be... just remember that if anyone asks you for R_average, find the R at a single point (using V=IR). And if someone asks for R_dynamic, just pick two points that surround the point they're interested in, find the slope, and then report the inverse. Simple, no?
     
     So what good is all this average and dynamic resistance stuff? It's used to figure out if something is ohmic or not; if the average and dynamic resitances are not the same, then the sucker is non-ohmic.
3. Simple guide to Loop and Node rule: just remember that what goes in must come out and that in series, you add the voltages whereas in parallel, you add the current.
   
   What does it mean to have something in parallel or in series? Well, series is easy... if you remember from the first lab (just click the link to the left if your memory's half as hazy as mine), something is in series when you put it before or after the circuit element in consideration. But something is in parallel when it straddles it, e.g., when you put the voltmeter across a circuit element to get the voltage drop across it. Another way to look at it is to say that something is in parallel when it has a common connection with something else. That is, on our little circuit boards, if one end of each element (say, the positive end of 2 resistors) both go to the same hole (and the negative ends go to another common hole), then the 2 resistors would be considered to be in parallel.
   
   Put this way, the node rule seems eminently reasonable: as the same number of electrons enter a node (i.e, a common point), that same number must leave it. The stream of electrons might divide (one electron goes left from the common junction while the other goes right) but eventually both streams will meet up again at the other end (the other common point). Imagine two buddies following a trail, one after the other. They come to a fork in the road (our first junction); one path leads left while the other leads right. Our first guy goes left while his buddy goes right. Later on, the two paths of the fork meet up again and so do our errant friends. The two paths of the fork are the two lines of our circuit that are in parallel with each other.
   
   As for the series rule for voltages, think of an interrupted waterfall. Imagine that a waterfall falls from one height down to a level pool. As the pool overflows, the water flows out and falls off another edge down into the waiting river which flows off somewhere. A battery would be a water pump that pumps water from the river back up to the very top of the waterfall. Once there, the water has to fall back down. A resistor (or other circuit element) can be thought of as the intermediate pool (i.e., the little pool at the intermediate height between the very top and the river). If I look at the difference in height (and hence gravitational potential energy) between the very top and the very bottom (the river), I get the same amount of energy that the pump puts into the water that it's moving from the very bottom to the very top. But, if I measure the difference in height (and, once again, the corresponding gravitational potential energy) between the intermediate pool and the very bottom (still the river), that value is less than the full value. All that the loop rule says is that the sum of the height from the very top to the intermediate pool + the height from the intermediate pool to the very bottom (the river) = the total height from the very top to the very bottom (t + b = h, below). In electrical terms, the electrical potential energy across all the circuit elements of a circuit add up to the potential of the battery hooked to it.

   -- Top of Waterfall --     ____________________ -
                            ||        |            |
                            ||        |            |
                            ||        t (top half) |
                            ||        |            |
                            ||        |            |
                            ||        |            |
   -- Int. Pool --     _______        -            h (total height)
                     ||     |                      |
                     ||     |                      |
                     ||     |                      |
                     ||     b (bottom half)        |
                     ||     |                      |
                     ||     |                      |
                     ||     |                      |
   -- River -- ========     -                      -
   
   t + b = h
   

4. Just as in the first lab, be sure to use the Goldstar as the voltmeter and the Keithley as the ammeter.
5. Misc. stuff:
   1. On p. 30, instead of using 0.25V as the first reading, use 0.3V.
   2. For the 2nd part (Section 4.2), try setting the connections based on the circuit schematic alone and then use the detailed drawing as a check only. This will help you develop a feel for the last 2 circuits (the complicated part that might keep you in lab for 3 hours if you're not careful).
   3. Be sure to check your polarities (as in the first lab, you might want to imagine the battery pushing out simultaneously from both sides to figure out if something is positive or negative; e.g., in Fig. 7, the positive side pushes to the left while the negative side pushes simultaneously to the right so that the ammeter ends up having its left side as positive and its right side as negative).
   4. The 220W 1/4" resistor with an uncertainty of 5% has the following bands: red, red, brown, and gold. The 330W resistor is coded orange, orange, brown, and gold.
   5. Finally, for the last section, remember that the ammeter should be in series and that it replaces the wire (since the ammeter itself completes the circuit) in the portion you want to get a current reading at. If you leave the connecting wire in and just plug the ammeter on top of it, the current will simply follow the path of least resistance (the extraneous wire) and totally bypass the ammeter (thus resulting in a zero amps reading on the ammeter).
      
      I guess you can continue the waterfall analogy here: to measure how fast the falling water is falling (i.e., the water's current), you have to stick your measuring device right into the water at that point. But, if you want to measure the height, and hence the potential (in analogy with our electrical potential, the voltage), you can do it from the outside without interfering with the circuit (i.e., the waterfall). If this doesn't seem too clear, lemme know and I'll draw up some pictures that'll clarify the matter. Just remember that the ammeter needs to actually be a part of the circuit (measure speed of falling water) whereas the voltmeter needs to be outside the circuit (measure height of waterfall or basin from some distance).

1. Minor: on p. 35, last paragraph, tared should be rated in the 2nd to last line.

Required Materials:

1. Laboratory Manual (SGM 407)
2. Laboratory Answer Book
3. Calculator with statistical functions
4. Ruler

1. This lab has the potential to take a long time. The tricky part will be the last section where you're not given a detailed diagram of the circuit (just the schematic). So spend some time in looking at it and making sure you know where the different meters go.
2. Feedback on if you're finding these pages helpful (or not) is definitely good. So if you have any strong opinions, or, dare I say it, ideas on how to make this better, drop me a line!