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

• 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 circuitfor both

10 Watt 2*5 Watt

variables

• 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 12*5Watts 10Watts

Results- part 1

Clarification of results • 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

• 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 twenty-

four 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 twenty-

four 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• 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• 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

• 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.