Magnetic Fields unit test
A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.
Field of a finite wire segment
Ampère's law vs Biot-Savart
Field of a long straight wire
Field inside a solenoid
Field at the center of a circular loop
Biot-Savart law
Mass spectrometer
Force on a current-carrying wire
Magnetic dipole
Why magnetic force does no work
Force between parallel wires
Right-hand rules summary
Short answer 1. Define or explain: Magnetic force on a charge
3 ptsShort answer 2. Define or explain: Cyclotron frequency
3 ptsShort answer 3. Define or explain: Choosing an Ampèrian loop
3 ptsShort answer 4. Define or explain: Hall effect
3 ptsFree response
10 ptsStudents determine the number of turns per unit length of a long solenoid by measuring the magnetic field at its center with a Hall probe for several values of the current. I (A) 0.50 1.00 1.50 2.00 2.50 B (mT) 0.63 1.24 1.90 2.50 3.15
A(i). Explain why the probe must be positioned near the middle of the solenoid rather than near an end. A(ii). Describe one step that would reduce experimental uncertainty.
B(i). State the expression for the magnetic field inside a long solenoid and indicate what quantities the students should graph to obtain a straight line usable to determine the turn density. B(ii). State what the slope of that graph represents.
C(i). Describe the axis labels, with units, and the positions of the plotted points. C(ii). Describe the best-fit line, including what its vertical intercept should be and why.
D. Using the best-fit line described in part C, calculate an experimental value for the number of turns per unit length of the solenoid.