Midterm Exam Information

Location	THH 201
Date & Time	2/29/00 at 5pm

• What's it going to be like?
• What should I know?
• What should I bring?

• The exam will cover Experiments I-V only.
• The midterm is similar to the previous midterms... your best preparation for it is, without a doubt, reviewing the old exams. The old exams are available at: http://physics1.usc.edu/Undergraduate/Labs/135b/. As usual, pay particular attention to the exams going back to Spring 1998.
• The exam is closed book but most important formulas will be given (but not the trivial ones like V=IR!).
• The exam is scheduled for 2/29/00 in THH 201
• The lab written exam is setup as follows:
  1. You will have 1 ¹/₂ hours to finish approximately 8 questions.
  2. There will definitely be questions on:
     • DC Circuits and the various elements therein
     • Ammeters and Voltmeters (and how to use them)
     • Diodes and 1/2-wave rectifiers
     • Equipotential Fields
     • AC Circuits
  3. There is an equal mix between theory and computation; be prepared to look at familiar ideas in new settings. Also, this exam is probably more on the harder side so be sure to study hard!

• Introduction to Electric Circuits and Measurements -- Lab 1
  • Review the different circuit element symbols (Fig. 3 on p. 4)
  • Know the properties of an ideal ammeter and voltmeter (ideal ammeter offers 0 resistance whereas an ideal voltmeter has infinite resistance; why?)
  • How are they placed in circuits? Ammeters in series and voltmeters in parallel (see p. 6)
  • Make sure you understand how you setup and used the one and two battery circuits (pp. 7-8)
  • Know how to measure voltages across elements (e.g., across the bulb) or currents in a circuit (ammeter is placed in series, i.e., before or after the circuit element)
• Mapping the Electro-static Field -- Lab 2
  • Know the relationship between E & F (E = F/q)
  • Know the relationship between V & E (V = Ed)
  • Review the mechanical analogy between Voltage and Gravitational Potential Energy (V=W/q; W=DPE; V=DPE/q)
  • Be sure you understand the gravitational analogy (and especially make sure you understand the quiz questions & also Fig. 3 on p. 18)
  • How do E & V work in electrophoresis?
  • How does the Faraday Ice Pail work and what does it's equipotential field look like (review the diagrams in your answer book or the lab notes to the left)
  • Where was the electric field strongest in the Ice Pail? the weakest? Why?
• DC Circuits -- Lab 3
  • Recall Ohm's Law and the various derived formulas (e.g., V=IR; P=IV; etc. -- more listed in the lab notes for this lab)
  • Make sure you understand Kirchoff's rules (the node rule and the loop rule); review them in the manual or in the lab notes
  • Understand the difference between ohmic and non-ohmic materials (constant resistance vs. variable resistance; linear I vs. V graph versus non-linear I vs. V graph; etc.)
  • Be aware of the difference between R_avg and R_dynamic (see the lab notes). Make sure you know how they're calculated (see especially Fig. 1 on p. 24)
  • From p. 25 of the manual, what is I_max? What is the significance of it? How do you compute it?
  • Review resistance in series and in parallel; current in series and in parallel; voltage in series and in parallel (see the lab notes for these formulas -- be sure to understand the formulas and make sure you're able to apply them, too)
  • Some things to consider: how did you actually connect the resistors in series and in parallel? How did you measure V & I in the various configurations (for this part, review pp. 32-33 carefully)
• AC Circuits -- Lab 4
  • What is the power source in DC and AC circuits? Batteries or DC power supply in DC and the function generator in AC. What is the difference between alternating current and direct current? (See Fig. 1 on p. 38 for this guy)
  • Be very sure you completely understand the difference between peak current, peak-to-peak current, DC offset, and RMS current (see the lab notes for all of these). Where is RMS current applicable (sine waves ONLY!)? When is I_rms = I_o/sqrt(2) (see p. 39)? How do you get the period of a wave? How about the frequency?
  • For AC circuits, which values are used in the application of Ohm's and Kirchoff's laws? (the RMS values only). What values does the multimeter read?
  • Diodes -- Read ALL of p. 41!
  • Also, read pp. 51-53. Know how diodes work, what the output looks like, what it does in the 1/2-wave rectifier circuit (and how). In essence, make sure you understand what a diode does and how the oscilloscope output looks before and after putting the diode in the circuit (and, while you're at it, consider how the output changes when you mess with the diode or the circuit, as you did in question 4.3.2)
• Electronic Filters -- Lab 5
  • Know what a capacitor is and what it's electric field looks like (see also Lab II for this one)
  • How do V & I vary in a charging capacitor (see Fig. 3 on p. 65)? What is the time constant t? What is it's significance in terms of the charging/discharging capacitor (see Fig. 3 again)?
  • Make sure you know how the period, T, is related to the frequency, f, and the angular frequency, w (T = 1/f; 2pf=w)
  • Review the lab notes and be sure to understand the logic of the derivations of the different values we got in class.
  • What is I & V for a capacitor in an AC circuit? Does current lead V by 90^o (see the quiz or the lab notes if you're not sure)?
  • How does the capacitor act as a filter (see p. 67 for this one)?
  • For this one, I'd really make sure I understood the difference between high- and low-pass filters (memorize the table from the lab notes for this one)
  • What does a line filter do? How about a band-pass filter? Review the lab notes and your answer manual for this one! How did you make the composite filters (see p. 70)? How would you actually build this in practice (i.e., all at once, one after the other, etc.?)
• Make sure you review all the formulas and understand what is what in the main ones enough to be able to use them (e.g., does the R in lab 3 correspond to R_avg or R_dynamic)
• Remember to keep track of units during any calculations; perform unit conversions with care and keep an eye out for order of magnitude errors (e.g., if you're checking the line filter, is it for 60 Hz or 60 kHz?). Also, be VERY careful with the polarity (see lab 1's notes for checking polarity)
• Finally, work quickly but carefully... and the neater the work, the easier it is on the grader. If you're unsure of the answer but are sure of your reasoning leading up to the answer, go ahead and explain what you were trying to do or what you know. Often, that'll get you at least some partial credit (if your reasoning is correct, that is!). Always try to write down the correct units at all stages and check your intermediate results to make sure it makes sense. And, most importantly, remember to take a deep breath and relax! In the big scheme of things, this really isn't all that much... just your whole, entire future, is all...

1. Your calculator (don't leave home without it!)
2. Ruler or straight-edge
3. A pen or pencil (depending on how masochistic you are...)