Why does closing the switch cause the voltage across the thermistor to decrease?

AI Thread Summary
Closing the switch integrates the bulb into the circuit, reducing the overall resistance due to the parallel configuration. This change increases the total current flowing through the circuit. As the current increases, the voltage across the thermistor decreases because more current is diverted through the bulb. If the thermistor's resistance drops significantly, it could lead to the bulb turning off. The relationship between current, resistance, and voltage explains why the voltage across the thermistor falls when the switch is closed.
nokia8650
Messages
216
Reaction score
0
See attachment.

Question: "The switch S is now closed. Explain, without calculation, why the voltage across the
thermistor will fall"

I am able to deduce that by turning the switch on, the bulb becomes part of the circuit, effectively loweing the resistance of the parrallel "section" and hence the resisitance of the overall circuit. This will cause a greater current to flow. Why, however, will the voltage across the thermister fall? Thanks
 

Attachments

  • cir3.jpg
    cir3.jpg
    7.3 KB · Views: 432
Physics news on Phys.org
I can't see the picture so I don't know what the circuit looks like. Try uploading it to imageshack and putting in a link or something like that.
 
madmike159 said:
I can't see the picture so I don't know what the circuit looks like.

Sometimes it takes a while for a mentor to spot the attachment to approve it-- an hour's not bad going!
 
Wellif theresistanceof the thermistor was high then most of the current would go round via the bulb. If the resistance in the thermistor droped low enough then the bulb should go out.
 
Thread 'Collision of a bullet on a rod-string system: query'
In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
Thread 'A cylinder connected to a hanged mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top