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PRACTICE / Magnetic flux

Zero flux can still mean current

A fixed 40-turn coil has area 0.020 m² per turn and normal +z. Its resistance is 4 Ω. The uniform external field is B_z=(0.30−0.10t) T for time t in seconds.

At t=3.0 s, what is the signed current? Counterclockwise viewed from +z is positive.

Organize the givens & assumptions
  • 40 turns, 0.020 m² per turn
  • R=4 Ω
  • B_z=0.30−0.10t tesla

Flux is due to the stated external field; fixed area and orientation; coil inductance negligible; resistance constant.

  1. A00
  2. B−0.020 A-0.020\ \mathrm A
  3. C+0.020 A+0.020\ \mathrm A
  4. D+0.00050 A+0.00050\ \mathrm A

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