AP Physics C: Electricity & Magnetism 13.1 Magnetic Flux Questions

Analyse magnetic flux through arbitrary surfaces by combining field-area orientation, nonuniform integration, source superposition, changing overlap, and graphing.

Syllabus
Effective Fall 2024
Course
AP Physics C: Electricity & Magnetism

Exam points

  • determine magnetic-flux magnitude and sign from field strength, area, and surface orientation
  • integrate a spatially varying magnetic field over the portion of a surface it crosses
  • derive time- or position-dependent flux for a moving loop or changing magnetic source
  • combine signed flux contributions from multiple wires, regions, or field components
  • construct a piecewise magnetic-flux graph and label its signs, extrema, and transition points

Question 1

[Maximum number: 4]

A wire is connected to a resistor of resistance R to form a rigid rectangular loop of width L and height 2 L. An external force is exerted on the loop so that the loop always moves with constant speed v in the +x-direction, as shown in Figure 1. The loop then enters Region 1 of external uniform magnetic field of magnitude B that is directed in the -z-direction. Region 1 has boundaries x=L and x=2.5 L. The loop later enters Region 2 with two external, uniform magnetic fields, each of magnitude B, that are parallel but are directed in opposite z-directions. Region 2 has boundaries x=2.5 L and x=3.5 L. Point S is the midpoint of the leading edge of the loop and is aligned with the horizontal boundary in Region 2 that separates the two magnetic fields.

On the following axes, sketch a graph of the magnetic flux Φ\Phi through the rectangular loop as a function of the position x of Point S from x=0 to x=4.5 L. The +z-direction indicated in Figure 1 corresponds to +Φ+\Phi.

Figure for Question 1 — AP Physics C: Electricity & Magnetism
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