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A transformer has a primary coil with 400 turns connected to a 240 V AC supply and a secondary coil with 100 turns. If the secondary is connected to a 20 Ω resistor, the power in the secondary circuit is:

Correct answer: B. 180 W

  • A. 72 W
  • B. 180 W
  • C. 288 W
  • D. 360 W

Explanation

Voltage ratio Vs/Vp= Ns/Np. Thus, Vs= (100 / 400) × 240 = 60 V. CurrentIs =Vs/R= 60 / 20= 3A.Power P =VsIs=60×3=180 W, but adjusting for ideal transformer power conservation, P = (602/20) = 180 W.

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Magnetic flux density and magnetic flux describe the strength of a magnetic field and the field passing through a surface. A charged particle moving through a magnetic field experiences a force perpendicular to its velocity and may follow circular or helical motion, depending on the angle between velocity and field.

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