Practice Final Exam

Electron mass = 9.11x10^-31 kg

m_o = 4 p x 10^-7 N/A²

1.  One hundredth of a mole of ideal gas is at 27 ºC in a 240 cubic centimeter box.  What is the pressure?

2. A cruise ship uses a 600⁰C heat source to make steam to drive its turbines and dumps its waste heat into the ocean at a temperature of 27⁰C. The plant generates 1.2 x 10¹¹ J/hr of electricity and dumps 1.6 x 10¹¹ J/hr of heat into the river. How much heat per hour is absorbed at the higher temperature and what is the thermal efficiency of the plant? What is the maximum theoretical efficiency of the plant?

3.  A 2.4 microfarad capacitor is connected across an alternating voltage with an rms value of 9.0 volts.  The rms current is is 25 mA.  What is the frequency of the voltage source? 

4.  A power plant generates 800 MW of power at a voltage of 75 kV. Before leaving the power plant the electricity passes through a transformer with 48 turns on the primary and 480 turns on the secondary.  If the power line to the city has a resistance of 6 ohms, what is the power being lost on the power line?

5.  A radioactive material with a half-life of 4 seconds on earth has a half-life of 12 seconds as measured by an astronaut speeding by.  How fast is the astronaut moving relative to earth?

6.  What inductance is needed in a L-R-C circuit to allow a 300 pF capacitor and 5 kW resistor to be resonant at a frequency of 1.45x106 Hz?

7.  Answer the following questions for the expression v(t) = 70.0V cos (2pft)?

a.) What is the peak voltage?
b.) What is the voltage at 7.50ms if the frequency is 50.0 Hz?
c.) What is the rms voltage?
d.) If the peak current is 1.00A, what is the average power?

8.  An inductor has a voltage of 2V when a current flowing through it changes from 4 A to 6 A and requires 5 ms for the change.

a. What is the inductance, L, of the inductor?

b. What is the inductor's reactance at 4 MHz?

Fill in the blank with the appropriate word or words.

9.  The total entroy of the universe is always (increasing or decreasing) which leads to more (disorder or order).

10.  In an inductor, the current peaks ___________________ the voltage peaks.

11.  Einstein postulated the ________________ of physics are the same in all inertial reference frames and the _______________ of light in vacuum is the same in all inertial reference frames. Consequences of these postulates are the loss of _______________________ for events in all reference frames, ________________ contraction and ___________________ dilation.

12.  Magnetic fields are produced by electric charges that are ____________________.

13.  Dry skin has a resistance of 1 MW, wet skin 10 kW.  Would a person likely be in trouble grabbing a wire with a 1.00 kV AC voltage, with either wet or dry skin?

14.  A capacitor with reactance of 10.0 W at a frequency of 3.00 kHz, has a current of 10.0 mA when the voltage changes over a time of 1.00 ms.  What is the change in voltage?

15.  An object is 25 cm from a lens with a focal length of 10 cm.  How from from the lens is the image and on what side is the image?

16.  A light ray is traveling at 25 degrees to the normal of the surface in a material with an index of refraction being 2.  On the other side is glass with an index of 1.5.  What angle to the normal does the light ray make in the glass?

17.  State Einstein's postulates concerning the Laws of physics and the speed of light.  Describe how Galilean and Einstein's Special Relativity differ in how the speed of light transforms between two reference frames.

18.  If a spaceship is travelling 0.6 c, relative to Earth, who measures the proper period of the astronauts heart beat?  Who measures the proper length of the spacecraft?  Who measures the proper orbit of pluto?  If the spacecraft has a mass of 2 x 10⁶ kg what is the relativistic energy with respect to a mountain climber on Earth?

19.  Explain how electromagnetic waves propagate from the perspective of electric fields and magnetic fields  Be sure to include the field direction and the light propagation direction.

20.  What is the rest energy of an electron?  If the electron is moving at 0.6c, what is the kinetic energy? 

21.  An electron has a measured (relative to Earth) momentum of 1.33 x 10^-22 J.   What is it's relativistic energy and speed measured from Earth?

22  A electron travels in a region with uniform electric field of 30 N/c at an angle of 30 degrees from parallel to the field lines.  If it travels 1 km, what is the difference electric potential energy from start to finish?

23. A capacitor has 12 mC of charge and V_C = 1V and is disconnected from its surroundings. A medium with K = 2 is placed between the plates. What is the charge and voltage afterwards?