Will this work?

Discussion in 'General Electronics Chat' started by Lightfire, Aug 13, 2011.

  1. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010

    I want to know if this schematic will work in real life.:D

    Pls. look at the schematic I attached and judge if it will or not.:)


    P.S. It is a lamp. Ok. ty:)
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    The lamp will light up. The resistor needs to have at least 3W power dissipation (and it will get HOT), better 5W. Not very efficient...
    Lightfire likes this.
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    Sometimes resistive droppers are a necessary compromise, for instance to allow LEDs to be used safely from a fixed voltage supply. They may also help you learn practical applications of Ohm's Law, but they are wasteful. They turn electricity straight into heat.

    After all, the heating elements in electric heaters and some cookers act like resistors. That's fine if we want to heat up the house on a cold day, or maybe boil some potatoes, but generally we try to minimise the use of big hot resistors.
    Lightfire likes this.
  4. Audioguru

    AAC Fanatic!

    Dec 20, 2007
    The 39 ohm resistor will have about 9.8V across it so the current in the circuit will be only 251mA. The 300mA light bulb will appear to be dimmed a little.
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  5. SgtWookie


    Jul 17, 2007
    The resistor will waste a lot of power as heat; nearly 5 times as much power as will be used generating light in the bulb. The bulb will waste about 80% of the rest of the power generating heat.
    Lightfire likes this.