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Physical Science Lab

From Science Olympiad Student Center Event Wiki

Physical Science Lab Event Links
Forum Thread: 2009 2010

Test Exchange: 2009

This event involves the construction of a device that can turn wind into energy and the answering of questions relating to alternative energy. This also refers to the C division event Physics Lab. See the original Physics Lab page for information about the old event.

1 The Basics of the Event
2 The Building Section
3 Written Portion
- 3.1 Alternative Energy
- 3.2 Physics
  - 3.2.1 Energy
  - 3.2.2 Heat
4 The Competition
5 Scoring
6 Links

The Basics of the Event

Half of your score for Physical Science Lab is how well you do on the building. You have to create a wind turbine-like object using a CD and other materials. During competition, they will attach your device to a CD motor. You will then place a fan in front of your device and turn it on. Your blade will spin therefore creating voltage. The higher your voltage, the better your score. You must include a standard CD in your wind turbine.

The Building Section

When you plan to build your device, there are many factors to consider. Some of them include:

Wind turbine Diameter
Blade Width
Curve of the Blade
Blade Pitch
Number of Blades
Blade Material
Alteration of CD or not

Something else you might want to think about is how heavy your device is. If your device is lighter, it can spin faster, therefore producing more voltage. You can use various items to construct your blades. Balsa wood is sometimes used as it is very light. You could also find different items around your house to use as blades. Plastic cups, when cut in half, can be a good idea. You just have to experiment with different factors. According to the New York Coaches Conference, taller towers increase energy production. They also say that doubling the diameter of the circle made by the blades produces a 4-fold increase in power. For more information on good windmills, look at this site Turbine Designs. There are various pages here discussing turbine designs.

For the competition, you are allowed to bring in 2 devices. Also, make sure that your CD fan is at or under 30 cm in diameter

Written Portion

The other half of your score is the written portion. The rules recommend that you look at Alliant Energy and American Wind Energy Association. The main topics this year regard alternative energy and the physics of energy and heat. These topics involve several formulas.

Alternative Energy

Alternative energy is generally defined as energy that does not harm the environment directly. They usually do not produce carbon emissions and many times they are also renewable. There are several types of renewable energy, each with its own advantages and disadvantages.

Solar power converts sunlight into energy via photovoltaic panels or concentration. It is generally constant as the Sun will shine constantly for millions of years unless a catastrophic event occurs, but it is costly and clouds can interfere with the efficiency.
Wind power converts wind into energy, usually with turbines. Wind is plentiful and the method has no emissions, but turbines can be unwelcome both visually and environmentally. Also, periods of wind are more unpredictable than some other methods.
Hydroelectric power converts the movement of water into energy, generally with turbines as well. the flow of water is abundant, constant, and hydroelectric plants can store energy for times when it is more necessary, but there are concerns in respect to the reservoirs created by dams.
- Tidal power is a major subset of hydroelectric power. It uses the movement of water created by tides to get energy. Tides are regular and predictable, but less power can be generated this way than some other ways.
Ocean Thermal Energy Conversion (OTEC) utilizes the difference in temperature from shallow water to deeper water. When heat goes from the warmer water to cooler water, an engine converts the flow to energy. This is constant, but not very cost-effective and finding locations where this technology can be used is difficult.
- NOTE- In the rules, OTEC is listed as meaning Oceanic Tidal Energy Currents. This is incorrect, but event supervisors may still base their tests off of this incorrect denomination.
Geothermal power converts underground heat into energy. This method is reliable, cost-effective, and environmentally friendly, but is mostly limited to areas with a high tectonic activity.

To conserve energy, the adage "reduce, reuse, recycle" can be followed. These three concepts can be applied to many techniques used to conserve energy.

Physics

There is also a section in the rules regarding energy, work, and heat and heat transfer concepts.

Energy

Energy is the capacity to perform work. Work, in turn, is when a force is exerted on an object and the object moves parallel to the direction of the force. Work, in joules (J), can be calculated by multiplying the force applied in Newtons (N) to the distance traveled in meters (m). Power is the rate at which this work is performed, and is found by dividing the work by the time. It is measured in watts.

There are two major types of energy:

Kinetic energy is the energy contained by an object in motion
Potential energy is how much work an outside force like gravity can do on an object depending on its position.

The Conservation of Energy principle states that energy cannot be created nor destroyed, and that it can only be transformed from one form to another.

Heat

Heat is the transfer of energy from a high-temperature object to a low-temperature object.

Temperature

Temperature is the average energy contained in the particles of an object. It is produced by the thermal energy in free particles. Many scales can measure temperature.

Celsius scale
- was created in 1744
- is named after Anders Celsius
- bases its scale on the values of 0°C at water's freezing point and 100°C at water's boiling point
Fahrenheit scale
- was created by Daniel Fahrenheit in 1724
- Places water's freezing point at 32°F and its boiling point at 212°F so they are 180° apart.
Kelvin scale
- created by Lord Kelvin in 1848
- uses same scale as Celsius but puts 0 K at absolute zero (the hypothetical lowest temperature), making it always 273.15 units higher
- does not use ° symbol; is only K.
Rankine scale
- created by William Rankine in 1859
- is Kelvin-Celsius equivalent to Fahrenheit; 0 °R is absolute zero and it is always 459.67 degrees higher than °F.

An important conversion factor is that between Celsius and Fahrenheit, and vice versa. The calculations are:

$C=\frac {5}{9} \left ( F-32 \right )$

$F=\frac {9}{5} C 32$

Where C is the temperature in Celsius and F is the temperature in Fahrenheit.

Heat Transfer

There are three main vehicles for transferring heat:

Conduction is the transfer of heat by direct contact. The heat transfer for convection can be calculated by the following formula:

$Q=\frac {kA\left (T_{hot}-T_{cold}\right )}{d}$

Where

Q is the heat transferred in $Watts$

k is the barrier's thermal conductivity in $k=\frac {watts}{m K}$

A is the cross-sectional area in $m^2$

T is the temperature in °C ( $T_{hot}$ represents the warmer temperature and $T_{cold}$ represents the cooler temperature)

d is the barrier's length in $m}$

Conduction

Convection is the transfer of heat from a solid or liquid to another fluid. Forced convection is a fluid flowing over a surface. Natural convection is when a fluid is heated and rises due to bouyancy such as when hot air rises and cooler air sinks, creating circular currents. The heat transfer for convection can be calculated by the following formula:

$Q=hA(T_{hot}-T_{cold})$

Where

Q is the heat transferred in $Watts$

h is the film coefficient in $h=\frac{watts}{m^2 K}$

A is the surface area in contact with the fluid in $m^2$

T is the temperature in °C ( $T_{hot}$ represents the warmer temperature and $T_{cold}$ represents the cooler temperature)

Convection

Radiation is where the heat is carried by electromagnetic waves. The Stefan-Boltzmann Law can help calculate this transfer:

$P=e\sigma A \left (T^4-{T_C}^4\right )$

Where

P is the radiated power in $Watts$

e is the object's emissivity

σ is Stefan's constant (equal to $5.6703 \times 10^-8 \frac {W}{m^2K^4}$ )

A is the radiating area in $m^2$

T is the temperature of the radiating source in K and $T_C$ is the surrounding temperature.

Specific Heat

This is the amount of heat per unit mass needed to raise a substance's temperature by 1 °C. It is represented by the following formula:

$Q=cm\Delta T$

Where Q is the heat needed, c is the specific heat, m is the mass, and ΔT is the change in temperature.

The Competition

For the building set-up, there will be 2 stations: high speed and low speed. You will be given 5 minutes to set-up and test your device in front of each fan (5 minutes for high, 5 minutes for low). Once you are ready, you may tell the event supervisor to start the fan. The fan will run for one minute and the highest voltage within the time frame will be recorded as your score.

Once you have completed the device testing, you will get 40 minutes to complete the stations/written part.

Scoring

For this event, the highest score wins. Your voltage score is calculated like this:

Voltage Score = Low speed voltage (mV) + High speed voltage (mV)
Test Score = based on a 50 point scale (if you have 25 questions, each is worth 2 points.)

Final Score = 50 x (Part I score)/(Highest Part I score of all teams) + Station Score (50 point base)

The tiebreaker is the team that has the best high-speed performance.