EXPERIMENT No. 4

                       10 Volts                                                               15 Volts

volt drop V1 :  3.978 v                                                                   3.978 v

volt drop V2 :  0.743 v                                                                   0.745 v

volt drop V3 :  4.521 v                                                                   4.744 v

volt drop V4 :  5.763 v                                                                   10.53 v

calculated current A: 10 amps                                                         15 A

Describe what is happening and why you are getting these readings?

V1 = 3.978 because zener diode is reverse bias. V2 is 0.7 v because that is the knee voltage.
V3 = V1 + V2 = 4.521. V4 = 5.763 the zener in reverse bias in kneeds 5 v to get to break down voltage + the 0.7of the other diode = 5.763. With the 15 v curcuit the zener and other diode 1N4007 take 5.53 v so the resistor will use up the rest which is 10v.