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Physics 2B Exam Instructions and Questions, Exams of Physics

The instructions and questions for a physics 2b exam. The exam covers various topics in physics, including magnetic fields, electric charges, generators, and magnetic flux. Conversion factors and constants for reference. Students are allowed to use handwritten notes and calculators during the exam, and are required to show their work and include units with each answer.

Typology: Exams

Pre 2010

Uploaded on 07/30/2009

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Physics 2B 12/05/20
PHYSICS 2B
October 24, 2001
Name:____________________
Rules for Exam:
1. You are allowed one 3"x5" sheet of handwritten crib notes. You MUST turn in
your crib notes.
2. Calculators are allowed, but you may not share one.
3. Show your work on numerical problems. Do not expect any credit for a problem
if I cannot logically follow what you have put on your paper.
4. Make sure you include units with each answer. One point will be deducted for
each infraction.
5. Points will be deducted for students that refuse to turn in their exams, when
asked to do so (at the end of class).
6. In general you will not be penalized for incorrect sig. figs. However, one point
will be deducted for each answer that has a ridiculous amount of significant
figures. For example, a final answer quoted as 2.239389479 m/s is ridiculous.
7. Circle your final answers.
There 7 pages to this exam. Put your name on all pages of the exam.
Good Luck!
________________________________________________________
Conversion Factors and Constants:
1 mile= 5280 feet (exact) 1 day= 24 hours (exact)
1 inch= 2.54 cm (exact) 1 hour=60 minutes (exact)
1 cm= 10 mm (exact) micro (=10-6
1 eV=1.602x10-19J
Magnitude of the charge on the electron and proton, or ion 1.602x10-19 C
k 8.99x109N-m2/C2
Permittivity of free space 8.85x10-12 C2/ N-m2
Mass of proton 1.67x10-27kg
PART 1 (22 points)
PROBLEM 1
PROBLEM 2
PROBLEM 3
TOTAL (65 max)
PERCENTAGE (out of
60)
1
pf3
pf4
pf5

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PHYSICS 2B

October 24, 2001

Name:____________________

Rules for Exam:

1. You are allowed one 3"x5" sheet of handwritten crib notes. You MUST turn in

your crib notes.

2. Calculators are allowed, but you may not share one.

3. Show your work on numerical problems. Do not expect any credit for a problem

if I cannot logically follow what you have put on your paper.

4. Make sure you include units with each answer. One point will be deducted for

each infraction.

5. Points will be deducted for students that refuse to turn in their exams, when

asked to do so (at the end of class).

6. In general you will not be penalized for incorrect sig. figs. However, one point

will be deducted for each answer that has a ridiculous amount of significant

figures. For example, a final answer quoted as 2.239389479 m/s is ridiculous.

7. Circle your final answers.

There 7 pages to this exam. Put your name on all pages of the exam.

Good Luck!

________________________________________________________

Conversion Factors and Constants: 1 mile= 5280 feet (exact) 1 day= 24 hours (exact) 1 inch= 2.54 cm (exact) 1 hour=60 minutes (exact) 1 cm= 10 mm (exact) micro (=10- 1 eV=1.602x10-19J Magnitude of the charge on the electron and proton, or ion 1.602x10-19^ C k 8.99x10^9 N-m^2 /C^2 Permittivity of free space 8.85x10-12^ C^2 / N-m^2 Mass of proton 1.67x10-27kg PART 1 (22 points) PROBLEM 1 PROBLEM 2 PROBLEM 3 TOTAL (65 max) PERCENTAGE (out of 60)

Fill in the blank, short answer, and multiple choice. (2 points each, unless

otherwise noted).

  1. Which one of the following statements concerning the magnetic force on a charged particle in a magnetic field is true? A. It is a maximum if the particle is stationary. B. It is zero if the particle moves perpendicular to the field. C. It is a maximum if the particle moves parallel to the field. D. It acts in the direction of motion for a positively charged particle. E. It depends on the component of the particle's velocity that is perpendicular to the field.
  2. An electron is placed into a magnetic field that points to the right. If the velocity of this electron is toward the top of the page as it enters the magnetic field, the force on it is directed A. toward the bottom of the page B. toward the top of the page C. to the left D. into the page E. out of the page
  3. Which one of the following statements best explains why a constant magnetic field can do no work on a moving charged particle? A. The magnetic field is conservative. B. The magnetic force is a velocity dependent force. C. The magnetic field is a vector and work is a scalar quantity. D. The magnetic force is always perpendicular to the velocity of the particle. E. The electric field associated with the particle cancels the effect of the magnetic field on the particle.
  4. Two loops carry equal currents I in the same direction. They are held in the positions shown in the figure and project above and below the plane of the paper. The point P lies exactly halfway between them on the line that joins their centers. The centers of the loops and the point P lie in the plane of the paper. Which one of the figures below shows the position of a compass needle if the compass were placed in the plane of the paper at P?
  5. The magnetic flux through a steel door is equal to  when the normal to the door is parallel to a uniform magnetic field. What is the angle between the magnetic field vector and the normal to the door if magnetic flux drop to 1/2 of its original value? A. 15  B. 30  C. 60  D. 90 

Name:____________________

Problems

Do three of the following four problems. If you attempt all the problems, CLEARLY

indicate the three you want graded. Otherwise, the first three solved problems will be graded.

You are not allowed to change your choice after turning in your

exam.

  1. One important application of negative ions is that they can be used to eliminate 14 N contamination in 14 C for dating biological and geological samples. The reason why this is useful is that nitrogen atoms can’t form a negative ion. A 14 C-^ beam is selected after the ions that emerge from the accelerator and traverse a mass spectrometer. Suppose we want to select 14 C-^ beam that has a kinetic energy of 3.0x10^4 eV from the accelerator. The radius of the beam’s path through the spectrometer is 0.50 m. Calculate the magnetic field that is required to select the 14 C-^ beam. (12 points). Note: A negative ion is atom with an extra electron attached to it. The atom 14 N is a nitrogen atom with an atomic mass is that is approximately 14 times the mass of the proton. 0.19T
  1. A long, straight wire carries a 10.0-A current in the +y direction as shown in the figure. What is the magnitude of the net magnetic force that acts on the loop? What is the direction of the net magnetic force that acts on the loop? (15 points) 0.000017N
  1. A loop is pulled with a force F upward, a distance of .037 meters in 0.0080s. The loop has a length of 0.23 m, a width of 0.09 m, and a resistance of 350.0 . At the instant shown (after 0.008s elapsed), the loop is partially in and partially out of a uniform magnetic field that is directed into the paper. The magnitude of the field is 0.8 T. a. What is the magnitude of the emf induced in the loop? (5 points)? 0.33V a. What is the induced current in the loop (3 points)? 0.94mA b. Calculate the force F required to pull the loop if it moved at a constant speed. (5 points) 0.000068N