PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Five separate, identical circular conducting loops (labeled A–E) lie flat on a horizontal table. For each loop, the magnetic field at the center is perpendicular to the plane of the loop. The table below describes how the magnitude and direction (into or out of the table) of the magnetic field at each loop changes over a short time interval of equal duration.
• Loop A: field directed into the table, magnitude decreasing.
• Loop B: field directed into the table, magnitude increasing.
• Loop C: field directed out of the table, magnitude increasing.
• Loop D: field directed out of the table, magnitude decreasing.
• Loop E: field magnitude remains constant at zero.
(a) For each loop A–E, state whether the induced current is clockwise, counter-clockwise, or zero as viewed from above. Provide a concise justification for each answer based on the change in magnetic flux.
(b) Rank the magnitudes of the induced emf in loops A–E from largest to smallest. If any are equal, indicate that explicitly. Explain the reasoning that leads to your ranking without performing numerical calculations.