A student is provided with a 2 V cell, a lamp, a switch and a thermistor with a negative temperature coefficient of resistance. The lamp, which is in series with the cell as in Figure 1, lights immediately the switch is turned on.
Explain why (a) when the thermistor is connected in series with the lamp, as in Figure 2, and the switch is turned on, the lamp lights up slowly, and (b) if the lamp is omitted, as in Figure 3, and the switch is turned on, the cell is soon destroyed by overheating.
2. The attempt at a solution
We have a NTC thermistor, whose resistance decreases with the increase in temperature. I'm still not sure whether I got the usage of this apparatus. It is used in order not to create large voltage rises for the devices like lamps. Is it correct?
(a) If my understanding of this devide is corrrect, than the lamp lights slowly because the thermistor slowly passes the current from the 2 V cell.
(b) If the resistance of the thermistor decreases with the increase in its temperature, then over time it will have no resistance and the battery will ovearheat itself?
Where am I wrong / correct?