Conceptual Physics

1.( Describe two things that waves do that particles (like balls and boxes) don’t. Give the technical names and then explain how they work and how they’re observed.

Waves are characterized by defined properties such as amplitude, wavelength, frequency and speed. However, particles are defined by their masses and other measurable characteristics. Waves can go around obstacles while particles cannot. For instance, in a shooting spree, one can take cover behind the wall and will not be hit by the bullets. However, it the shooting person screams, one is still able to hear while in hiding. The sound waves have traveled through the obstacles so that one hears. Also, waves have the extent of space meaning that they are everywhere, but particles are localized. The observation of a cork on water, when disturbed, shows the waves of water forming certain patterns while the cork remains at the same position.

2. Look at the periodic table to answer this one and the next one (you may get a google image of this or use your book). Polonium (Po) decays to lead (Pb). What kind of radiation was produced? How do you know? (Justify your answer.)

When polonium decays to lead, it leads to an alpha radiation. This is because the mass number changes from 218 to 214. The change is a loss of 4 protons that indicate the alpha particle production.

218Po --------------- 214Pb + 4He

The emission of the helium nucleus indicates the alpha decay that results in mass number reduction by 4 as seen above.

3. Another periodic table question. Astatine (At) decays to radon (Rn – don’t confuse it with radium, which is Ra). What kind of radiation was produced? How do you know?

This type of decay is not possible. Astatine-221 cannot decay to Radon-222. For an alpha decay to occur, four protons have to be lost to create a helium nucleus. Also, for a beta decay, a loss of proton or neutron has to occur. In this case, what is seen is a loss of mass number by 1 and a loss of atomic number by 1.

4. At the most basic level, what produces magnetic fields?

A volume of space that experiences any change in energy is referred to as a magnetic field. When an electron rotates on its electron path around the nucleus, it creates a magnetic field. The moving electrons are charged particle thereby creating a magnetic field. However, when the charged particle is static, it does not create a magnetic field. The moving electron creates a change in space that leads to the generation of a magnetic field.

5. Why do we use high-voltage lines to transfer our power from the power plant to our homes and businesses?

The high-voltage lines help in improving efficiency by reducing the loss of heat along the wires. This does not reach the homes and business directly as it may lead to accidents for those close to the lines. However, the high voltage power is passed through a step-down transformer before reaching our home. The step-down transformer converts the high voltage into manageable levels that can be transmitted to the homes.

7. (Over the course of 10 days, the average American family home uses 288 kW-hr of energy. A.) How much power is that family using, on average? (step one: how many hours in 10 days?) b.) How much current is that family using, on average, knowing that the voltage coming out of the wall for them is about 120V?

Power = Energy/time

1 kW-h =3,600,00 joules

24kW-hr = 86,400,000 joules

Power = 86,400,000 joules/ (10 x 24 x 3600)

= 100 Watts

Current = power/voltage

= 100/120

= 0.8333 Amperes

8. Why can’t nuclear fission power plants explode like a bomb?

This is because the solid used in nuclear fission is natural uranium that is not explosive in nature. The natural uranium occurs as a combination of two isotopes U-235 and U-238. The highest percentage is U-238 that is very poor in neutron-induced fission in any given conditions. As such it cannot take part in any chain reaction. However, U-235 is reactive and can undergo fission. For a bomb to be made out of the nuclear material, the percentage of U-235 has to be increased to above 90% for it to explode. It is for this reason that a nuclear fission plant cannot explode like a bomb.

9. Briefly, what are the most problematic issues associated with power from nuclear fission? Why would nuclear fusion be so preferable to nuclear fission, if only we could get it to work as a power source here on earth?

Nuclear fission is associated with an increase in radioactive wastes through disposal as well as a contribution to nuclear weapon proliferation. The nuclear fission reactors release radioactive materials as waste products that are carcinogenic and can affect the people around the reactors. Also, the continuous use of uranium could pose the risk of nuclear weapon proliferation that is harmful to the world.

Nuclear fusion leads to the production of increased energy as compared to nuclear fission. The reaction needed in nuclear fusion is simple as it needs getting the fuel as hot as possible in containment to enable the components to fuse. However, it has been difficult to achieve the right magnetic field making it impossible to use it here.

10. (Earthquakes produce waves in the rock of the earth. A. What kinds of waves are produced? Which are the fastest? The most dangerous? B. What do earthquakes tell us about the interior of the earth? How do we figure that out?

The main kinds of waves generated by earthquakes include the P waves, S waves, Love waves, Rayleigh waves, body waves, and surface waves. The fastest waves are the P waves. The strongest waves are the surface waves.

Earthquakes show that the inner of the earth had some stored energy in elastic risks that are suddenly released. The outburst of energy leads to shaking of the earth near the source of the release leading to an earthquake. The earthquakes tell us that the interior of the earth is not constant in terms of temperature, pressure and composition. The different properties of the layers of the earth, as well as the rocks, present make the earthquakes occur. By understanding the seismic tomography as well as seismic wave velocities, it is easier to predict the likelihood of an earthquake in a certain area.

11.) What are the transformers that you personally own or use? How do they work? Why are they necessary?

Transformers are used to reduce the voltage that is passed through a system. A simple transformer is used in the use to control the amount of voltage reaching the gadgets. This is to prevent damage in the case that power surges occur. The adapter used to plug in the sockets before charging a laptop or a phone have inbuilt transformers that reduce the voltage that reaches the gadgets. Transformers prevent any accidents due to increased voltages.

Long Answer

12.— be sure your answer is thorough! that’s a lot of points!) The AC/DC debate between Edison and Tesla was partially about how centrally energy should be generated (one big power plant for the city, or one on every block), and that’s coming up again now. As individual residents and businesses can have solar power and wind power, energy generation may be getting less centralized. What are the pros and cons of having centrally generated power vs. locally generated power, and are these the same or different than in the old AC/DC debate? (Be sure to talk about how each of these kinds of power is generated and transmitted.) What model do you think we should focus on going forward?

Centrally generated power refers to the use of the classic grid system to distribute power to various points according to the required voltages. The method uses infrastructure and electrical transmission to deliver electricity at the points where it is needed. This has been the tradition method where transmission lines are used to distribute the power. As a result, a lot of costs is used for the infrastructure to create above-ground transmission lines. Also, after construction, maintenance costs are required which shows that expensive nature of the grid operations. In areas with damaging storms, the transmission lines are dangerous to the population. The high tension lines can also be disastrous in highly populated areas.

Locally generated power is however provided at the point of use. The use of distributed generation has allowed enhancement of security. Also, there has been increasing in the reliability and power quality. This is due to the reduced surges that are common in transmission and distribution as a result of the distances. The locally generated power has the advantage of avoiding power losses that occur due to the use of power lines. It has been indicated that about 8-10 % of the power generated centrally is lost during transmission. Similarly, distributed power uses micro-grid applications that can operate independently of the electric grid to balance the intermittent renewable generation of power. Lastly, the locally generated systems will allow a reduction in congestion by allowing the classic transmission and distribution capacities to be applied by renewable sources such as solar and wind energy generation.

The debate on AC/DC represents the same dilemma as in the use of centrally or distributed networks. The logic of applying a better method that saves up on the costs of transmission is seen here. Moving forward, it is crucial to adapt the locally generated power as the advantages outweigh those of the centrally placed. Also, the risks posed are less making it more favorable and economical.