Re: 12 volt 7amp/h versus10amp/h ??

The resistance of filament lamps is current dependent. I think you'd
have a better comparison test if used used a fixed value resistor.

Although it is true the resistance of a lamp changes with applied voltage,
it is not an issue since the current flowing through a fixed resistor will
change as the voltage decreases. As the voltage decreases, current
decreases. As a matter of fact, as the voltage on the lamp decreases, the
temperature of the filament will decrease, which will decrease the
resistance, which will increase the current drawn. Thus, the lamp should
result in more constant current flow and improve the accuracy of a constant
current graph.

If you start at a certain voltage and discharge to a defined ending voltage,
it should not matter whether your resistance is slightly variableor fixed.
In neither case will you have a constant discharge, which is often what the
hypothetical battery discharge graph imagines.

I have used lamps successfully for years to check out batteries. The secret
is to select a lamp with the same current draw as the equipment you are
using. You can glance over at the lamp and see that all is well.

Colin



.

Relevant Pages

  • Re: Poll (& me being boring)
    ... one hand is on the metal of the lamp. ... > Where V is the voltage, I is the current and R is the resistance. ... both hands wet gripping a 1.5 inch pipe (pretty close to the actual ...
    (uk.rec.humour)
  • Re: a better incandescent light bulb
    ... Your model shows a net reduction of voltage available to the bulb. ... you changed R1 to a linear resistance. ... But the voltmeter was connected only across the lamp, ... to determine how an unmodified filament behaves when the voltage ...
    (rec.crafts.metalworking)
  • Re: 12 volt 7amp/h versus10amp/h ??
    ... Although it is true the resistance of a lamp changes with applied voltage, it is not an issue since the current flowing through a fixed resistor will change as the voltage decreases. ...
    (rec.aviation.soaring)
  • Re: AC sine wave: What does increasing the frequency do?
    ... >>Which brings up the concept that an incandescent lamp appears to have ... >that changes is the resistance of the lamp filament. ... resistance peaking later than the voltage peak. ... which looks like a capacitive component. ...
    (sci.electronics.basics)
  • Re: quick question about watts.
    ... >the cooler it is the less resistance it has, ... pulling less amps is from less voltage. ... But with a lightbulb, resistance decreases as voltage decreases, so as ...
    (sci.electronics.basics)