Physics II

Time and Date Stamps (logged): 17:12:20 06-10-2020 ｰｶ涓ｱ浤ｯｯｵ涓ｯ浤ｯｱｯ Physics II

University Physics (Phy 232, Phy 242) Test 3

Completely document your work and your reasoning.

You will be graded on your documentation, your reasoning, and the correctness of your conclusions.

** Write clearly in dark pencil or ink, on one side of the paper only. **

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Name and Signature of Student _____________________________

Signed by Attendant, with Current Date and Time: ______________________

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Instructions:

Test is to be taken without reference to text or outside notes.
Graphing Calculator is allowed, as is blank paper or testing center paper.
No time limit but test is to be taken in one sitting.
Please place completed test in Dave Smith's folder, OR mail to Dave Smith, Science and Engineering, Va. Highlands CC, Abingdon, Va., 24212-0828 OR email copy of document to dsmith@vhcc.edu, OR fax to 276-739-2590. Test must be returned by individual or agency supervising test. Test is not to be returned to student after it has been taken. Student may, if proctor deems it feasible, make and retain a copy of the test..

Directions for Student:

Completely document your work.
Numerical answers should be correct to 3 significant figures. You may round off given numerical information to a precision consistent with this standard.
Undocumented and unjustified answers may be counted wrong, and in the case of two-choice or limited-choice answers (e.g., true-false or yes-no) will be counted wrong. Undocumented and unjustified answers, if wrong, never get partial credit. So show your work and explain your reasoning.
Due to a scanner malfunction and other errors some test items may be hard to read, incomplete or even illegible. If this is judged by the instructor to be the case you will not be penalized for these items, but if you complete them and if they help your grade they will be counted. Therefore it is to your advantage to attempt to complete them, if necessary sensibly filling in any questionable parts.
Please write on one side of paper only, and staple test pages together.

Test Problems:

. . . . . . . . . . . . . . . .

Constants

Constants:

k = 9*10^9 N m^2 / C^2	qE = 1.6 * 10^-19 C	h = 6.63 * 10^-34 J s
energy of n=1 orbital in hydrogen atom: -13.6 eV	k ' = 9 * 10^-7 T m / amp	atomic mass unit: 1.66 * 10^-27 kg
electron mass: 9.11 * 10^-31 kg	speed of light: 3 * 10^8 m/s	Avogadro's Number: 6.023 * 10^-23 particles/mole
Gas Constant: R = 8.31 J / (mole K)	proton mass: 1.6726 * 10^-27 kg	neutron mass: 1.6749 * 10^-27 kg

Problem Number 1

A proton (mass 1.67 * 10^-27 kg) with velocity directed to the North passes through a magnetic field of .0088 Tesla directed vertically upward, crossed with an electric field of 19000 N/C directed either East or West. The electron passes through undeflected. Is the electric field directed East or West, and how fast is the electron moving? What force does the electron experience from each field?

Problem Number 2

A uniform magnetic field with strength .0033 Tesla surrounds a coil consisting of 34 nearly coplanar circular loops of wire each of radius .26 meters. The coil is rotated about an axis which runs through its center and which lies in the plane of the coil; the magnetic field being perpendicular to this axis. If the coil is rotated at 84 Hz, what is the average voltage induced around the coil?

Problem Number 3

A square loop with area A and carrying current I lies initially stationary in a horizontal plane and is constrained to rotate about an axis parallel to two of its sides and passing through the center of the square. A vertical uniform magnetic field B permeates the region. If the loop has moment of inertia J, then what differential equation relates the angular position `theta of the loop to clock time?

Problem Number 4

Find at the point ( 19 m, -19.01 m) the direction and magnitude of the electric field due to a charge of 18 `microC located at ( 25 m,-28.01 m).

Problem Number 5

Problem Number 6

Find an expression for the work done in moving a test charge between plates, the potential difference between the plates, and the capacitance of a parallel-plate capacitor with uniform separation d and plate area A when the plates carry charges of Q and -Q. Repeat for a cylindrical capacitor of length L, inner radius r1 and outer radius r2, also carrying charges Q and -Q on the respective cylinders (University Physics students find exact expressions; others use a reasonable approximation).

Problem Number 7

A capacitor with capacitance 5 `microC/Volt is in series with a resistance of 45 Ohms. It is charged to 58 `microC, then the source is turned off, allowing the capacitor to discharge through the resistor.

How much current will be flowing at the instant the capacitor begins to discharge?

How long will it take the capacitor to release 1% of its charge?

How much energy will be discharged during this time?

Problem Number 8

Use integration to find the electric field due to a thin conducting disk of radius a on which a charge Q is uniformly distributed, at a point lying at distance z directly above the center of the loop.

Problem Number 9

An electrostatic field of magnitude 7.4 N/C makes an angle of 84 degrees with a perpendicular to the plane of a circular region whose radius is 4.8 meters. What is the electrostatic flux through the region?

Problem Number 10

A spacecraft moving at constant velocity .85 * c relative to a nonaccelerating observer keeps time by reflecting a light pulse back and forth between two mirrors oriented at a right angle to the direction of motion. The mirrors are 110 meters apart (big spaceship) and are mounted within a sealed vertical vacuum tube (vertical being perpendicular to the direction of motion) so that the light pulse will travel at its vaccuum speed.

If we assume that the laws of physics are the same in the reference frame of the spaceship as in the frame of the observer, it follows that the speed of light in a vacuum will be identical in both reference frames.

Under this assumption:

How long does it take a pulse to travel from the lower mirror to the higher, as measured in the spaceship?
How long does it take the pulse to travel from the lower mirror to the higher as measured by the observer outside the spaceship?
If the pulse rate of an inhabitant of the spaceship is 77 beats/minute, as measured by that individual, then what pulse rate would be measured by the outside observer, assuming some accurate means of making the observation?