PrayogX › Physics › Electromagnetic Induction

Conducting loops rotating through a half-plane magnetic field: the induced current of each loop matched to its graph

Four loops turn clockwise about O with a field only for x > 0. The current follows how fast loop area crosses the field boundary: P constant then reversed (3), Q two pulses each way (2), R a pulse in and out (1), S zero because one lobe enters as the other leaves (4) - option C.

Sub-topics covered

• Faraday's law: emf = -dPhi/dt, with Phi = B x (area inside the field)
• A rotating sector's straight edge sweeps area at r^2 omega/2 while crossing the field boundary
• No crossing, no current: a loop wholly inside or outside the field
• Lenz's law and the sign of the current; lobes of one loop that circulate the same way

What it teaches

• Only the part of a loop inside x > 0 carries flux, so i ~ dA_in/dt
• P half-disc: area enters steadily for half a turn and leaves for the next: + constant then - constant (3)
• Q two sectors: + T/6 pulse, gap, + pulse, then - pulse, gap, - pulse (2); R one sector: a pulse in at the start and a pulse out after T/2 (1)
• S two opposite sectors: one crosses out as the other crosses in; both lobes circulate the same way, so the flux is constant and i = 0 (4); opposite senses would add, not cancel
• P3 Q2 R1 S4: option C

Simulation ID

• ADV-2026-P1-PHY-Q15 · revision 1

See this simulation in the library →  ·  open the simulation file on its own