Challenges in the current fiber laser technology.

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If there is a cavity inside a conductor with no charge in it, what is the electric field in there?

What is Faraday’s ice pail experiment?

What is the work principle of Van de Graaff electrostatic generator?

What is electrostatic shielding?

Why lightning bolts are vertical?

A hollow conducting sphere has no net charge. There is a positive point charge at the center of the spherical cavity within the sphere. You connect a conducting wire from the outside of the sphere to ground. Will you measure an electric field outside the sphere? Explain.

This problem has 3 parts.

A single resistor with resistance R ohms is connected to a battery.

part a - If the single resistor is replaced with 2 identical resistors each of R ohms connected in series, will the battery have to provide more power, less power or the same? Explain your choice, include any equations that apply.

part b If instead of connecting the two resistors in series, they are connected in parallel, will the battery have to provide more power, less power or the same power as with the single resistor? Explain your choice, include any equations that apply.

part c If you compare the currents through each of the circuits: original circuit, part a circuit and part b circuit, will any of the circuits have a current larger than the other two or will they be the same. Explain your choice, include any equations that apply.

A sample of silicon is doped with donors to a concentration of 10^20 donors m−3 . Assume all the donors are ionised and that the sample is initially at 300K. (a) What is the concentration of holes in this sample of silicon? (b) Calculate the position of the Fermi level in this doped sample of silicon. (c) At what temperature will the intrinsic electron concentration become larger than the donor electron concentration?

There are three ways that radiating light can interact with matter. (a)List those 
processes and Illustrate each processes using simple two level system. (b) which 
one is the basis of lasing? (c) In that (lasing) process, explain why emitted photon 
has the same phase, polarization and direction as the exciting photon.

1. For each of the cases that follow, draw a picture of the system being described and list as many properties of the equilibrium state as you can, especially the constraints placed on the equilibrium state of the system by its surroundings.

a. The system is placed in thermal contact with a thermostatic bath maintained at temperature T.

b. The system is contained in a constant-volume container and thermally and mechanically isolated from its surroundings.

c. The system is contained in a frictionless piston and cylinder that is exposed to an atmosphere at pressure P and thermally isolated from its surroundings.

d. The system is contained in a frictionless piston and cylinder that is exposed to an atmosphere at pressure P and is in thermal contact with a thermostatic bath maintained at temperature T.

e. The system consists of two insulated tanks of gas connected by tubing. A valve between the two tanks is fully opened for a short time and then closed. (Note: Think through carefully about the consequences of the tank being opened for a short time instead of a long time – what would the difference be in the properties (T and P) of the gas in the two tanks?).

Calculate the magnetic field outside a straight conductor of radius R. Include drawing, if apply.

Suppose you first walk 10.5 m in a direction 20° west of north and then 25 m in a direction 40° south of west as shown in the figure.

a. What is the component of your displacement in the x-direction?

b. What is the component of your displacement in the y-direction?

c. How far are you from your starting point?

d. What is the angle of a line connecting your starting position to your final position, measured South of West, in degrees?

This problem has 3 parts.

The power company wants to deliver electrical service of 110 volts plus or minus 5 volts (105 to 115 volts), at 60 hertz frequency across a 10 kilometer transmission line to a small town. The transmission line voltage is 4,000 volts. There is a transformer available with a primary coil of 15,000 turns and secondary coils of 82 , 132, 164 and 187 turns.

part a - Which, if any, of the secondary coils can be used to deliver the power within the 105 to 115 volt range, include your calculations

part b - If a transformer is used that delivers an exact 110 volts, and the town requires a peak (maximum) of 800 kilowatts of power, how much current will flow through the 10 kilometer transmission line during the peak.

part c - Is a transformer has a secondary coil of 220 turns, how many turns are needed on the primary coil to get the 110 volts with an error of less than 1 percent?

Answer Questions 2.3.

2.3 Devise hypothesis to account for the following observations, and design an experiment or suggest further observations to test your hypothesis.

1. More automobile accidents occur at dusk than at any other time of day
2. When glass tumblers are washed in hot soapsuds and then immediately transferred face downward onto a cool, flat surface, bubbles at first appear on the outside rim, expanding outward. In a few seconds they reverse, go under the rim, and expand inside the glass tumbler
3. In mice of strain A, cancer develops in every animal living longer than 18 months. Mice of strain B do not develop cancer. If the young of each strain are transferred to mothers of the other strain immediately after birth, cancer does not develop in the switched strain A animals, but it does develop in the switched strain B animals living longer than 18 months.

Jack and Zack are standing on a crate at rest on a frictionless horizontal surface. Jack has a mass of 70 kg, Zack has a mass of 45 kg, and the crate has a mass of 15 kg. In what follows, we will see that both jump of the crate. You may assume that they push themselves off with a speed of 4 m/s relative to the crate and in a direction that is essentially horizontal.

1) what is the final speed of the crate if Jack and Zack jump simultaneously, in the same direction?

2) what is the final speed of the crate if Jack and Zack jump simultaneously, in opposite directions?

3) what is the final speed of the crate if Jack jumps first and Zack jumps a few seconds later, in the opposite direction as Jack?

Consider a thin uniform disk of mass M and radius R. A mass m is located along the axis of the disk at a distance z from the center of the disk. The gravitational force on the mass m (in terms of m, M, R, G, and z) is

A 70.0 kg70.0 kg ice hockey goalie, originally at rest, has a 0.280 kg0.280 kg hockey puck slapped at him at a velocity of 33.5 m/s.33.5 m/s. Suppose the goalie and the puck have an elastic collision, and the puck is reflected back in the direction from which it came. What would the final velocities ?goalievgoalie and ?puckvpuck of the goalie and the puck, respectively, be in this case? Assume that the collision is completely elastic.

?goalie=vgoalie=

m/sm/s

?puck=vpuck=

m/sm/s

Q

At very low temperatures, the specific heats of gases can change; they get smaller, almost as if some degrees of freedom get “frozen out.” Explain, using the simple harmonic oscillator as a guide, how this might happen.