Magnetism and Electromagnetism 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.
Generators and transformers
Magnetic field of a wire
Domains and ferromagnetism
Lenz's law IS energy conservation
Magnetic force does no work
Why the force is zero along the field
Eddy currents
Mass spectrometer
Force on a moving charge
Faraday's law
Magnetic flux
The Fv against ε²/R check
Short answer 1. Define or explain: Why power is transmitted at high voltage
3 ptsShort answer 2. Define or explain: Radius of circular motion
3 ptsShort answer 3. Define or explain: Negative charges: solve then flip
3 ptsShort answer 4. Define or explain: Applying Lenz's law to a falling magnet
3 ptsFree response
10 ptsMATHEMATICAL ROUTINES (Question 1, 10 points). Very long Wire 1 carries current I in the +x-direction along the line y = 0. Very long Wire 2 carries current I in the +x-direction along the line y = +d. Point P is located on Wire 1 at the origin. The wires' diameters are small compared to d, and both wires are in the xy-plane (Figure 1). For A(ii): very long Wire 3, carrying current 2I in the −x-direction, is placed in the xy-plane along the line y = y3 above Wire 2. The net magnetic force exerted on Wire 1 by the currents in Wires 2 and 3 is zero. For B: Wire 3 is moved very far away. A circular conducting loop in the xy-plane is initially held at rest below Wire 1, then moved at constant speed in the −y-direction, away from the wires (Figure 4).
A(i). Indicate the direction of the magnetic field from Wire 2 at Point P, and the direction of the magnetic force exerted on Wire 1 by Wire 2 (use directions such as into/out of the page, +y, −y).
A(ii). Derive an expression for y3 in terms of d. Begin with a fundamental physics principle or an equation from the reference information.
B. Indicate whether there is a clockwise induced current, a counterclockwise induced current, or no induced current in the loop, and justify your answer.