basic electronics

Discussion in 'General Electronics Chat' started by raj vivek singh, Jan 14, 2014.

  1. raj vivek singh

    Thread Starter New Member

    Jan 10, 2014
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    HI I am connecting 100 ohm resistor through 9v battery to base of transistor (bc 337),resistor become hot .so any one can tell me the reason
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    If you're not already familiar with resistance and Ohm's Law, research those.
    The base-emitter junction of the transistor drops about 0.8V at the current you're passing through it. So 9-0.8 = 8.2V is dropped across the resistor. The resistor (and base) current is therefore 8.2V divided by 100 = .082 Amps (= 82mA). The power wasted in the resistor as heat is current times voltage, = 8.2 x 0.082 = 0.67 Watts.
    Note that 82mA is also rather high for base current. Your resistor value should be much higher.
     
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  3. wayneh

    Expert

    Sep 9, 2010
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    Ohms law shows that 9-0.7 = 8.3 volts across a 100Ω resistor passes 0.083A. The power dissipated in the resistor is I^2•R, or 0.083^2•100 = 0.69W.

    That was enough to make it hot. If it was rated to anything less than 2W or so, it was probably very hot.

    Gaaaa...too slow for Alec
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    .... only by 17 min :).
     
  5. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Just adding on to what wayneh and alec said, Chances are you're only using a 1/4 or 1/2 watt resistor. So dissipating 0.6+ watts in it is going to cause it to heat up quite a bit, if not burn it out completely.
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The next question, what is connected to the emitter and base of that transistor? The base is already applying a 82 ma load! but that means the transistor is saturated and not restricting any current from flowing from emitter to collector. This means that the load resistance is the only thing restricting current flow from e to c and causing additional heating of the poor little transistor.
     
  7. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Could you post the circuit?
     
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Is this how the world "learns" now?
    Just attach a bunch of parts/plug it in and hope it does something.. if it doesn't then post on the internet asking for why?
     
  9. crutschow

    Expert

    Mar 14, 2008
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    Perhaps so. It may be related to how young people learn about computers and computer games. They just start pushing buttons until it works. :rolleyes:
     
  10. GopherT

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    It is how my son learned electronics. He was here 4 years before me and since moved on. He was in 8th grade at the time. By the way, thanks everyone for helping him build his first project. Apparently you all helped him solder, source parts and bias a tube amp. He presented the finished project to me as a surprise when I got home from an extended business trip. He plays the guitar but he wanted to build it on his own and surprise me. Apparently I tend to take over projects when my hands are around.
     
  11. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Who was your son?
     
  12. IcedFruits

    Member

    Jan 15, 2014
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    i connected a led to the mains when was in school. knew it was gonna burst, so switched on from 20 ft away, and so it did bust into pieces..... it was fun. :D

    but connecting things randomly without knowing the result is dangerous and may cause serious injury.
     
  13. raj vivek singh

    Thread Starter New Member

    Jan 10, 2014
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    i have bc 337-25transistor .i want to know the beta value of it ,i also looked at the data sheet but i didnt find there,and in 337 -25 what 25 signify and how we know the my transistor is made by which company (like philips or other one)
     
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