Transcript Incandescent bulb

Pandav, Concollato, Johns, Rahman
Aim
Materials
Aim
Method
Results
Discussion
Conclusion
To (a) determine whether one 10 W light bulb shines
better than two 5 W light bulbs, to (b) determine how a
small change in supplied voltage affects light emission,
and to (c) determine how a small change in supplied
voltage affects a light bulb’s lifetime.
Aim
Materials
Method
Results
Discussion
Conclusion
Variables involved
Controlled
Independent
Dependent
Distance between
luxmeter and bulb
Types of bulbs used
Light intensity (Lux)
Environment the bulb
is in
Number of bulbs used
External lighting
conditions
Voltage supplied to
bulbs
Circuit used for each
bulb
Aim
Materials
Method
Materials and equipment
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
Materials and equipment
2 x 5 W incandescent lamp
1 x lux-meter
1 x 10 W incandescent lamp
1 x spectrometer
2 x 12 V power supply
1 x ruler
4 x voltmeter
1 x cylindrical cardboard tube
2 x ammeter
Wires to connect the circuit
2 x variable resistor (rheostat)
Access to a computer
4 x retort stand with clamp
Access to a dark room
Aim
Materials
Method
Results
Discussion
Conclusion
PART A
1. The following circuits were set up next to each other. For the
first trial, only one 10 W light globe was set up, on one
circuit. The other circuit remained open.
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
PART A
2. A cylindrical tube was set up as follows, over the 10 W light
bulb. The apparatus was held in place using a retort stand.
Aim
Materials
Method
Results
Discussion
Conclusion
PART A
This setup allowed us to keep the distance between the light
bulb and the sensors constant.
Aim
Materials
Method
Results
Discussion
Conclusion
PART A
Aim
Materials
Method
Results
Discussion
Conclusion
3. The luxmeter and spectrometer were both connected to a
laptop, where SPARKvue was used to analyse data.
4. The brightness setting of the laptop was set to a minimum,
and the screen was bent down and turned away from the
apparatus so that it didn’t interfere with results.
5. The lights were turned off.
6. The 10 W light bulb was turned on for one minute, and the
following data was recorded:
• Light intensity over time
• Light intensity of various wavelengths of the
electromagnetic spectrum
PART A
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
PART A
7. For the second trial, two 5 W light globes were set up, one on
the circuit on the left, and another on the right. The two
circuits are identical.
Aim
Materials
Method
Results
Discussion
Conclusion
PART A
8. A cylindrical tube was set up as follows, over the two 5 W
light bulbs, which were placed right next to each other.
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
PART A
The same steps used for the single 10 W light bulb were
repeated with the two 5 W light bulbs.
9. The luxmeter and spectrometer were both connected to a
laptop, where SPARKvue was used to analyse data.
10.The brightness setting of the laptop was set to a minimum,
and the screen was bent down and turned away from the
apparatus so that it didn’t interfere with results.
11.The lights were turned off.
12.The 5 W light bulbs were turned on for one minute, and the
following data was recorded:
• Light intensity over time
• Light intensity of various wavelengths of the
electromagnetic spectrum
Aim
Materials
Method
Results
Discussion
Conclusion
PART A
The following are the results obtained for the single 10 W light
bulb.
Current (A)
0.751
Voltage across the power supply (V)
11.57
Voltage across the light bulb (V)
11.00
Mean light intensity (Lux)
1373 ± 70
NOTE: 70 is the standard deviation of the trial, which went for a
minute.
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
PART A
The following are the results obtained for the two 5 W light
bulbs.
Left
Right
Current (A)
0.372
0.366
Voltage across the power
supply (V)
11.64
11.59
Voltage across the light
bulb (V)
11.52
11.50
Mean light intensity (Lux)
1288 ± 93
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
Part B continued on from Part A, using the same circuits.
PART B
For the single 10 W bulb:
1. After the single-bulb trial in Part A was finished, the
resistance on the rheostat was increased in such a way that
the voltage across the light bulb decreased by 0.5 V.
2. The lights were turned off.
3. The 10 W light bulb was turned on for one minute, and the
following data was recorded:
• Light intensity over time
• Light intensity of various wavelengths of the
electromagnetic spectrum
Aim
Materials
Method
Results
Discussion
Conclusion
Part B continued on from Part A, using the same circuits.
PART B
For the two 5 W bulbs:
1. After the double-bulb trial in Part A was finished, the
resistance on both rheostats was increased in such a way that
the voltage across each light bulb was decreased by 0.5 V.
2. The lights were turned off.
3. The 5 W light bulbs were turned on for one minute, and the
following data was recorded:
• Light intensity over time
• Light intensity of various wavelengths of the
electromagnetic spectrum
Aim
Materials
Method
Results
Discussion
Conclusion
The following are the results obtained for the single 10 W light
bulb.
PART B
Mean light intensity (Lux)
1373 ± 70
The following are the results obtained for the single 10 W light
bulb after the voltage was decreased by 0.5 V.
Mean light intensity (Lux)
1235 ± 64
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
The following are the results obtained for the two 5 W light
bulbs.
PART B
Mean light intensity (Lux)
1288 ± 93
The following are the results obtained for the two 5 W light
bulbs after the voltage was decreased by 0.5 V.
Mean light intensity (Lux)
1158 ± 78
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
We performed some preliminary trials without the cylindrical tube first.
The rest of the method was the same. The sensors were each held in
place using retort stands and clamps.
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
Some preliminary trials were performed without the cylindrical tube first.
The rest of the method was identical. The sensors were each held in
place using retort stands and clamps.
Aim
Materials
Method
Results
Discussion
Conclusion
There was a lot of variation in our results, because it was difficult to
position the luxmeter at the same angle each time, using just the retort
stands. This resulted in a large standard deviation.
Aim
Materials
Method
Results
Discussion
Conclusion
The bulb(s) and the luxmeter were then fixed in place inside the tube, in
order to eliminate this problem.
Aim
Materials
Method
Results
Discussion
Conclusion
The following are the results obtained for the single 10 W light
bulb.
PART A
Mean light intensity (Lux)
1373 ± 70
The following are the results obtained for the two 5 W light
bulbs.
Mean light intensity (Lux)
1288 ± 93
Using these results, it can be seen that a single 10 W light
bulb shines brighter than two 5 W light bulbs.
Aim
Materials
Method
Results
Discussion
Conclusion
The following are the results obtained for the single 10 W light
bulb during the preliminary trials.
PART A
Mean light intensity (Lux)
1508 ± 67
The following are the results obtained for the two 5 W light
bulbs during the preliminary trials.
Mean light intensity (Lux)
1101 ± 205
The results from the preliminary trials also indicate that a
single 10 W light bulb shines brighter than two 5 W light
bulbs.
Aim
Materials
Method
Results
Discussion
Conclusion
The following are the results obtained for the single 10 W light
bulb.
PART B
Mean light intensity (Lux)
1373 ± 70
The following are the results obtained for the single 10 W light
bulb after the voltage was decreased by 0.5 V.
Mean light intensity (Lux)
1235 ± 64
This suggests that a decrease in voltage leads to a decrease
in light intensity.
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
The following are the results obtained for the two 5 W light
bulbs.
PART B
Mean light intensity (Lux)
1288 ± 93
The following are the results obtained for the two 5 W light
bulbs after the voltage was decreased by 0.5 V.
Mean light intensity (Lux)
1158 ± 78
This also suggests that a decrease in voltage results in a
decrease in light intensity.
Aim
Materials
Method
Results
Discussion
Conclusion
Aim
Materials
Method
Results
Discussion
Conclusion
The following is a suggested method for Part C.
PART C
1. Set up an external thermometer so that it is 1 cm away from
a 5 W light bulb, and is pointing at the bulb’s filament. Use
the same circuit outlined previously. The light bulb should be
5 W at 6 V.
Aim
Materials
Method
Results
Discussion
Conclusion
PART C
The following is a suggested method for Part C.
2. Gradually decrease the resistance of the rheostat, hence
increasing the voltage supplied to the light bulb, until the
fuse blows. Record the temperature at which the fuse blows.
3. Set up two identical 5 W bulbs, each with different voltages
supplied to them. Leave these on continuously for 72 hours.
4. After the 72 hours have elapsed, measure the temperature of
the filament of each globe to observe which globe is closest
to the temperature at which the fuse blew in Step 2.
Steps 3 and 4 could be repeated to get a wide range of voltages,
and hence see how each voltage affects the lifetime of the bulb.
Aim
Materials
Method
Results
Discussion
Conclusion
A 10 W light bulb shines brighter than two 5
W light bulbs.
As the voltage supplied to a light bulb
decreases, the intensity of the light it
produces also decreases.
Aim
Materials
Method
Results
Discussion
Conclusion
References
Woolf, L (n.d.). Seeing the Light: The Physics and Materials Science of the
Incandescent Light Bulb. Retrieved on October 30, 2013 from ,
http://www.sci-ed-ga.org/modules/materialscience/light/index.html>
Cornell University (April 3, 2000). Light Source Spectra. Retrieved on
November 2, 2013 from
http://www.graphics.cornell.edu/online/measurements/sourcespectra/index.html
Covington, E (n.d.). Early Incandescent Lamps. Retrieved on November 4,
2013 from <http://home.frognet.net/~ejcov/>