# Need confirmation on lightbulb experiment

1. Oct 2, 2012

### Flyingwing12

I was piddling with my meter and graphing calculator and came up with this equation

y= .08x+.14

This equation uses the number of batteries for X, and the Amp draw through a light bulb for Y.

The results are theoretical past 4 batteries.

The batteries were 1.29 v when the experiment began.

The real question here is about resistance.

Outside here it is about 80 degrees F, the ohmmeter showed 1.3 ohms from the light-bulb. The light bulb, using Ohms law, will have a resistance of ~11.4667 ohms when ~5.16 V are put to it. Meaning an amp draw of ~.45A

*With this initial resistance and final resistance being known, can I use a linear model to find the resistance of the bulb for each individual cell?*

How would this model be constructed?

If a graph were to be constructed it would start at (0,1.3) and end at (4, 11.46667). Is there any digital way of finding the missing values?

Kind of a math question isn't it?

Last edited: Oct 2, 2012
2. Oct 3, 2012

### es1

See part 2 in this link. It describes exactly your experiment, even uses your method of force voltage with batteries, and how to plot out the v vs i curve and what not.

http://teachers.usd497.org/agleue/unit_pdfs/electricity_unit_1/electricity_unit_1_ohm_laws_and_light_bulb_lab.pdf [Broken]

Last edited by a moderator: May 6, 2017
3. Oct 3, 2012

### es1

btw, i found this via a google when looking for the v vs i of a light bulb over this voltage range. here the bulb's large signal behavior isn't ohmic so it can't be modeled accurately over this range with an equation of the form y=mx+b.

you'll see all that, and an explanation, in the results section of the link above.