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PRACTICE / Alternating-current generator

Maximum flux is not maximum induced emf

A rigid 50-turn coil of area 0.020 m² rotates uniformly at 40 rad/s in a uniform 0.20 T field. Let θ be the angle between the positive coil normal and B, increasing with time.

What is the signed induced emf at θ = π/6 for the positive circulation linked to that normal?

Organize the givens & assumptions
  • N = 50
  • A = 0.020 m²
  • B = 0.20 T
  • ω = 40 rad/s
  • θ = π/6

Ideal rotating coil, uniform field, negligible self-inductance for computing the prescribed emf; flux linkage is NAB cosθ and the positive circulation follows the stated area normal.

  1. A+8 V+8\ \mathrm V
  2. B−4 V-4\ \mathrm V
  3. C43 V4\sqrt3\ \mathrm V
  4. D+4 V+4\ \mathrm V

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