Calculate Collector Current w/ Emitter @ 100mA - Transistor Switch

[Jason7fd]

Homework Statement

http://img300.imageshack.us/img300/2640/17569077cy5.jpg
The transistor is a N-P-N type. When the siren is functional, the resistance of thermistor is 120 ohm. R1 is 600 ohm. The question is "Calculate the collector current if the emitter current is 100mA". I know that current of emitter = current of collector + current of base, but how do I find the base current? Another one, "what is the maximum voltage across R1 if the siren is functional?".

Homework Equations

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The Attempt at a Solution

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[Defennder]

You didn't provide the value of R2. Also you didn't specify which end of the BJT is the emitter or collector. Is the BJT functioning in forward-active mode?

 

[Jason7fd]

You didn't provide the value of R2. Also you didn't specify which end of the BJT is the emitter or collector. Is the BJT functioning in forward-active mode?

I have updated the schematic diagram. Sorry, I am not sure what are BJT and forward-active mode. The value of R2 is not provided in this question.

 

[Defennder]

Uh, how are you expected to do this question if you don't know how a bipolar junction transistor (BJT) works in circuits? Do you know the equation for collector current in terms of V_BE? What is value of B, the beta parameter of the BJT?

 

[Jason7fd]

Uh, how are you expected to do this question if you don't know how a bipolar junction transistor (BJT) works in circuits? Do you know the equation for collector current in terms of V_BE? What is value of B, the beta parameter of the BJT?

I wish I was taught about this in school but they are not in the syllabus. It is a question from O-level Physics of Malaysia.

 

[Defennder]

Hi, could you post the question exactly as it is ? Because what you have provided so far is insufficient.