A Brighter Bulb – Sample Lab Report
Testable Question:
What can affect the brightness of a light bulb and how can you make the light bulb brighter?
Hypothesis:
Independent Variable: Testing a simple circuit with different numbers of batteries
Dependent Variable: The brightness of the light bulb
Control Variable: Same wires, same bulb, same brand of batteries, same length of wire
If I use 4 batteries, then the light bulb will be brighter.
Materials List:
2 wires approximately 20 cm long
1 mini light bulb
1 light bulb holder
2 brass wire clips
3 Duracell Batteries
Light bulb brightness scale
Data Table
Pen/Pencil
Ruler
Wire Cutters
Procedure:
1. Gather all of your materials.
2. Cut your two pieces of wire to a length of 20 cm.
3. Make sure that you have 1 cm of metal sticking out of the insulation of the wire. Use
the wire cutters/strippers to make the wire the correct length.
4. Connect the end of one of the wires (Wire A) to one of the clips on the light bulb
holder.
5. Connect one end of the other wire (Wire B) to the other end of the light bulb holder.
6. Screw the light bulb into the light bulb holder.
7. Connect the other end of Wire A to a wire clip.
8. Connect the other end of Wire B to the other wire clip.
9. Place 1 Duracell Battery between the wire clips, making sure to touch one of the wire
clips to the negative end of the battery and touch one wire clip to the positive end of
the battery.
10. Record the brightness of the light bulb using the Brightness Scale on your data table.
11. Keeping the same circuit, add 1 more battery to the circuit so that you are testing the
strength of 2 batteries.
12. Make sure that the batteries are connected negative to positive sides touching.
13. Record the brightness of the light bulb using the Brightness Scale on your data table.
14. Keeping the same circuit, add 1 more battery to the circuit so that you are testing the
strength of 3 batteries.
15. Record the brightness of the light bulb using the Brightness Scale on your data table.
16. Keeping the same circuit, add 1 more battery to the circuit so that you are testing the
strength of 4 batteries.
17. Record the brightness of the light bulb using the Brightness Scale on your data table.
18. Disconnect the circuit and put your supplies away.
19. Graph your data using a bar graph.
20. Compare and analyze you data and write your conclusion.
Brightness Scale
Off
0
Very
Very
Dim
1
Very
Dim
Dim
Bright
Very
Bright
2
3
4
5
Very
Very
Bright
6
Data Table
Number of Batteries
1 Battery
2 Batteries
3 Batteries
4 Batteries
Brightness on a Scale of 0 to 6
2
3
5
0
Data Analysis
Brightness of Light Bulbs with Number of Batteries
6
5
4
3
2
1
0
1 Battery
2 Batteries
3 Batteries
4 Batteries
Brightness
The circuit with 1 battery had a brightness of 2. The circuit with 2 batteries had a
brightness of 3. The circuit with 3 batteries had a brightness of 5. The circuit with 4 batteries
had a brightness of 0 because the bulb burned out. The circuit with 3 batteries had the brightest
bulb.
Conclusion
I reject my hypothesis that if I use 4 batteries, then the light bulb will be brighter. My
experiment showed that using 3 batteries showed the brightest light bulb. Using 4 batteries was
too much energy for the light bulb to handle and the light bulb burned out. My graph showed
that if the number of batteries are increased, the brightness will increase, but only to a point,
because the more batteries are putting more electrical energy into the light bulb. There is only so
much energy a light bulb can handle before it will burn out.