The Curve Tracer

As observed in the curve tracer experiment, the current lags the voltage, and the voltage is said to lead the current, when an ac sine wave goes through an inductor. (Doing the experiment requires two transformers, so it will not be performed here.) The relationship is shown in Fig. 10.8. Actually, the pendulum on page 98... 

Another type of avalanche diode is the "diac." This also has a characteristic curve that is the same in both directions, because it is a symmetrical design with a PNP structure. It can be thought of as two PN diodes, back to back. Each one is designed to be able to avalanche at about 1 ma of current without being damaged. Breakdown can be as low as about 6 volts, and this goes lower after the avalanche has started, even more so than in the neon bulb. We will make use of this device in Chapter 21. As an optional experiment, it can be inserted into the curve tracer to give a curve like that in Fig. 14.4. 

---