It is seen that number three compares favorably with the overshooting as shown by number two and the candle power corresponding was found to be approximately 50% greater than normal. It is not claimed that every lamp will overshoot this amount as the degree of vacuum or other factors of individual lamps may play an important part in this phenomenon. There is no doubt, however, that this strange fact really occurs and is not due to physiological reasons.
VIII. CURVES OF “OVERSHOOTING”.
In order to prove that the law of resistances, namely, R = Ro(1 + αt) does not hold for the first instance after closing the switch on a tungsten lamp, the following curves have been plotted. Number [V.] has been taken from the oscillograph record shown in the first part of this paper and shows that about .024 second elapses before the current becomes normal. Knowing the current at any instant as given by this curve, it is easy to find the resistance at the same instant by Ohm's law, the electromotive force being a constant and known value. Curve [VI] shows this relation. Curves [VII] and [VIII] are approximate values and not absolute. Now from the temperature curve, values are taken and substituted in the formula for resistance, R = Ro(1 + αt), the resulting curve being Figure [IX]. It is seen that curves [VI] and [IX] do not take the same values at all until after a brief interval of time has elapsed. Curve [VI] is absolutely correct, however, as these values have been obtained from the oscillograph record. Consequently, the assumption upon which curve [IX] is based must be incorrect for the first .024th of a second and the conclusion is that the law of resistances does not hold. This result tends to strengthen the theory of the lag of resistivity for the “overshooting” of a tungsten lamp.
Fig V
Fig VI
Fig VII
