Experiment 2
Now that we can light one bulb with one cell, what happens when we light one bulb with two or more cells?
STEP 1: Add a length of wire to one end of your bulb because you will need a longer length of wire to do these next experiment.
STEP 2: Choose what sort of cell you want to use. I decided on AA cells because I had them handy. If you have three C cells, D cells or AAA cells you could use those instead. Make sure whatever cells you choose that each works the same, so test them by lighting your bulb with each one.
STEP 3. Take note of the bulb's brightness with one cell. Next add a cell so that they are in "series." Series means that the positive of one battery touches the negative of another.
Try the bulb with two cells in series:
Note the brightness of the bulb.
STEP 4. Confirm that the cells need to be arranged like the diagram above by putting the cells together incorrectly:
Step 3. Use two cells in series. They should look like this:
How does the bulb glow when you have the cells configured this way? (If you get them backwards then the electrical current goes in opposite directions and will cancel one another out!)
STEP 5. Now try three cells in series. Remember that they would be connected the proper way as in STEP 3. You may need to tape the cells together to hold them unless you have more than one set of hands!
Note the brightness of the bulb. What happens as you keep adding cells to the brightness of the bulb?
Discussion. Each cell has a potential to do electrical work of 1.5 Volts. When we add cells in series, the potential is additive. Two cells are 3 Volts, 3 cells are 4.5 Volts. Every new 1.5 Volt cell would add to the voltage. You can think of voltage like pressure in a hose from a water tank. If the tank is short, there is little pressure. The taller the tank, the greater the pressure:
Each cell we add increases the potential energy of the "battery." The term battery refers to a series of cells connected to created more voltage. The single "cell" is just one 1.5 volt energy source.
STEP 6. What is a 9 volt battery then?
Let's do the arithmetic:
1.5V + 1.5V = 3 Volts
1.5 V + 1.5 V + 1.5 V = 4.5 Volts.
So how many cells in a 9 volt battery?
9v / 1.5 = 6 cells
If you take apart a 9 volt battery, guess what you will find?
Different configurations of six cells. The first two above are flat cells and the last one shows three small tubular cells and three more are behind those. You could always make a nine volt battery with 6 D, C, AA or AAA cells if you wanted! Just connect them in series.
STEP 7. What would you expect would happen if we connected our bulb to a 9 volt battery?
What do you think will happen?
Wow! Bright! I thought we may blow the filament in this little bulb!
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