light bulb theory

[soon2bdropped]

okay we was measuring voltage drop in a series circuit of a light bulb.. now when the bulb say blows.. how does the voltage drops to 12v still if theres no resistance because its blown... when we did the voltage drop test there was 12v before the lamp but 0v after the lamp(because the circuit is incomplete because of the blown bulb)



what i think is theres still powering getting to the bulb but none after it.. so is it still a live circuit before the bulb and not after.. help me out here buddy..


electrical class suck..

[Aeromech]

With the bulb before it is blown, you have a closed circuit...current flows from power to the bulb and to the ground or negative side of the battery(whichever one you are using)

When the bulb blows, the filament inside it breaks and you have an open circuit(much like turning a switch to the "off" position)

Series circuit with bulb and switch

When the bulb blows and you use your voltmeter, you should get 12V on one terminal and 0V on the other terminal on the bulb.

Keep in mind, when you use the voltmeter and get the 12V you are completing a circuit from the POS on the battery to the bulb and back through the voltmeter and back to the battery. When you get the 0V you are getting a circuit that is from the NEG on the battery to the bulb and back through the voltmeter and back to the battery.

I hope that helps....

[jhondayaaj]

well, voltages drop after the load. If you have 12v before the load, then 0.1 or more after the load, then that is normal (with the circuit being good and the switch closed that is). But if you have 12v before the load, and 0 v after the load, then you might have a bad load or a bad ground path. or in your case, a bad bulb.
well, 12 volt reference.

and voltage drop of 12 v. is the total voltage drop the same as your reference voltage?? yes. then the circuit is fine. you already know that the bulb is blown.
just remember, after the load should be 0.1 v or greater on a complete circuit. on a circuit that has an open will be 0v. hope that I helped.

[soon2bdropped]

how does a bulb with less resistance dimmer than a bulb with greater resistance?

i thought less resistance more voltage get thru..

more resistance.. less voltage can get thru.. or im mixing it up with amperage..


does this goes for series circuit or parallel? thanks