Spring Break 2010

It’s spring break this week. Instead of planning my trip to Cinemark Movies 14 I’m left with the thought of how I am I going to measure the amount of heat transfer from a light bulb to a body of water. Why? It’s a project in one of my classes this semester. The light bulb is powered by a 9V battery, and is encased in an insulated container along with a small pool of water that has a thermocouple in it. Right away I encounter some issues with this because finding a light bulb that is compatible with 9V is difficult.

My group wired two 4.8V light bulbs in series. This way the battery would be giving 4.5V to each bulb. We tried heating 50ml of water with the bulbs, but we couldn’t get a significant amount of temperature change because the lights weren’t getting hot enough. When I say significant I mean measureable. The power output of the bulbs was too low.

One requirement of our project is to measure the energy content in the 9V battery we are using in the experiment. The amount of Joules. Yes the battery is full of priceless, shiny Joules of energy. No not rubies or diamonds. The unfortunate truth is that a unit of energy itself is undetectable to the human eye. This leaves many scholars to question the concept of energy.

In order for us to measure the energy content of the battery we have to have a measureable amount of temperature change in the water. To achieve this we replaced our two series-connected light bulbs with one 12V car headlight bulb. We were now getting about a 1 degree change in celcius in ten minutes, but now the battery stops powering the bulb after about 25 minutes, while the battery itself still has charge in it. So how do we now determine the amount of charge that still remains?

We are required to use a 9V battery for the project. We have decided to measure the energy content via a different experiment, but the teacher might not approve. If anyone has any tips on how to wire this circuit so that we can get enough power out of the light bulbs to heat the water quickly, while at the same time draining the battery fully, please email me at studentjournalist1@gmail.com