Transcript Document

And then there was light.
A report on multiple experiments
concerning two five Watt incandescent
light bulbs and one ten Watt light bulb.
Liam King, Arthur Kyriakopoulos, Vincent Lu
Aim
• The first aim was to find out whether a ten
Watt light bulb would shine brighter than two
five Watt light bulbs.
• The second aim was to determine how the
lifetime of the bulbs would change if the
voltage was increased.
Hypotheses
• The first hypothesis is that the ten watt will
shine brighter, as less energy poses the risk of
being inefficiently converted.
• The second hypothesis is that the 10 Watt will
continue to emit higher levels of light, even
when it is not at the recommended voltage.
Materials for testing light
for both
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crocodile clips
A microscope box
Mini-stone slabs
A slim mobile phone
A Labdisc GenSci
Ten Watt and five Watt
light bulbs
• A power supply
Method-setting up the circuit
for both
10 Watt
2*5 Watt
variables
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Whether it is in parallel or series. Control
Type of wiring. control
The difference between manufacturers. Control
Vacuum or gas-filled. Control
Material the wire is made out of. Control
AC or DC Control
Voltage supplied. Dependent
Light emitted. independent
Wattage of bulb. Control
Current dependent
Ambient temperature control
Results- part 1
2*5Watts
10Watts
Results- part 1
Clarification of results
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The voltage of both circuits was 12 volts.
The two five watt light bulbs emitted 26 lux
The ten watt light bulb emitted 31 lux
Hence the 10 Watt is brighter
discussion
• These results are less than the manufacturer
of bulbs results, that is not a problem. As the
sensor was positioned in the same position
respective to the bulb; there is no problem in
concluding that the 10 Watt outputted more
light.
Theory of part 1
• The Lumens per Watt of an incandescent light bulb does not
increase linearly.
• A lumen is a measurement to measure light intensity.
• For example a typical 25-watt light bulb produces only 210 lumens
of light. A 100-watt light bulb produces 1600 lumens of light. It
requires about eight 25-watt bulbs to produce as much light as one
100-watt bulb. Therefore, a 100-watt bulb is twice as efficient as a
25-watt bulb.
• This correlation is true for the 5 and 10 Watt light bulbs.
• As the lumen efficacy of a 5 Watt bulb is 5 lm/w and the 10 Watt
bulb is 13 lm/w.
• Lumens = Watts * luminous efficacy
• The two five Watt: Lumens= (5*5)+(5*5)= 50
• The 10 Watt: lumens= 13*10= 130
Theory of part 1
• This phenomenon is explained by the: Stefan–Boltzmann law.
• It describes the power radiated from a black body in terms of
its temperature.
• Specifically, the Stefan–Boltzmann law states that the total
energy radiated per unit surface area of a black body across
all wavelengths per unit time is directly proportional to the
fourth power of the black body's thermodynamic
temperature.
Sources of error for part one
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Power surges
Ensconced bulbs
Incorrect readings from the voltmeter.
Inefficiency of the wiring
Whether the bulbs had been used before.
Starting temperature.
Method for part two
• The experiment is essential the same as the
first.
• Except the voltage is doubled to 24V, this was
verified by an external voltmeter.
Results- the 2*5Watt
Lux
Results- the initial flash
2 5Watt
10Watt
Clarification of results
the 2*5Watt light bulbs
• An input voltage of twentyfour volts.
• The lux increased over the
first 33 seconds.
• After it reached its peak the
light output decreased at
35.85 lux/second
The 10Watt light bulb
• An input voltage of twentyfour volts.
• The bulb blew almost
immediately.
• Initially it emitted a brighter
flash than the 2*5volt
experiment.
Theory of part 2
• The tungsten that is used to create the coil,
that provides the resistance that creates the
heat, will evaporate more quickly at higher
temperatures.
• And in section one through the use of Stefan–
Boltzmann law we have established the 10
Watt will reach higher temperatures.
Theory of part 2
5 Watt
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12v
P/V=I
I=5/12A=0.4167A
P=I^2 R
R=5/(0.4167)^2=28.8Ω
24v
P=V^2 /R
P=(24)^2/28.8=20W
P/V=I
I=20/24=0.8334A
10 Watt
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12v
P/V=I
I=10/12=0.8334A
V=RI
R=12/0.83=14.4Ω
24v
P=V^2/R
P=24^2/14.4=40W
P=I^2 R
I^2=40/14.4 I=1.6667A
• These calculations demonstrate that both circuits have the same current,
voltage, resistance and perform the same work.
• This strengthens points made in earlier slides, as although the ten Watt use
the same energy it is blown as it uses it more effectively( heats up to a
greater temperature.)
Sources of error for part 2
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Power surges
Ensconced bulbs
Incorrect readings from the voltmeter.
Inefficiency of the wiring
Whether the bulbs had been used before.
Starting temperature.
We couldn’t measure the initial flash, and can
only judge that it is brighter by eye.
conclusion
• The first hypothesis was correctly proved by the
luminous efficacy being higher in the 10 watt
than the 2 5 watt. This was also confirmed
through our results, where our reading for the
light levels of the 10 Watt were larger than those
of the 5 Watt light bulbs together.
• The second hypothesis was validated by the
blowing up of the 10 Watt bulb due to the greater
energy it transferred.
Real life conclusion
• The first experiment demonstrates it is more efficient
to have on large bulb than to half the size in parallel.
This will save in lighting costs.
• Therefore it will be better in a situation where high
light levels are important. For example a theatre.
• The second experiment puts forth the idea that if you
were using the lights in a situation where you could
have a power surge, the two smaller bulbs in parallel
would be favorable as the are less likely to blow.
• Hence this method should be used in a situation where
lighting is essential. For example an emergency exit.