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

In summary, the conversation discusses the effect of closing a switch on the voltage across a thermistor. The switch being closed causes the resistance of the overall circuit to decrease, resulting in a greater current flow. The discussion also touches upon the relationship between resistance and current in determining whether the bulb will stay lit or go out.
  • #1
nokia8650
218
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
 

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  • #2
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.
 
  • #3
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!
 
  • #4
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.
 

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

1. What is a potential divider?

A potential divider is a simple circuit that uses resistors in series to divide a voltage into smaller parts. It is commonly used in electronic circuits to provide a specific output voltage.

2. How do you calculate the output voltage in a potential divider?

The output voltage can be calculated using the formula Vout = Vin * (R2 / (R1 + R2)), where Vin is the input voltage and R1 and R2 are the values of the resistors in the potential divider.

3. What is the purpose of using a potential divider in a circuit?

The purpose of a potential divider is to provide a specific output voltage that is lower than the input voltage. This is useful in various electronic applications such as powering sensors, adjusting signal levels, and creating reference voltages.

4. Can a potential divider be used to increase voltage?

No, a potential divider can only divide a voltage into smaller parts. It cannot increase the voltage.

5. What is the effect of changing the values of resistors in a potential divider?

Changing the values of resistors in a potential divider will affect the output voltage. A higher value resistor will result in a larger output voltage, while a lower value resistor will result in a smaller output voltage.

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