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JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Magnetic Effects of Current

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Four identical long solenoids A, B, C and D are connected to each other as shown in the figure. If the magnetic field at the centre of A is 3 T ,the field at the centre of C would be: (Assume that the magnetic field is confined with in the volume of respective solenoid).
  1. (A)9 T
  2. (B)6 T
  3. (C)12 T
  4. (D)1 T✓ Correct

Answer: (D)

Solution

The field at the centre of a long solenoid is , so for four identical solenoids the field is proportional to the current each one carries. B, C and D are three identical branches connected between the same two nodes, and A is in series with that combination, so the current flowing through A splits equally and each of B, C and D carries . The field at the centre of A is T, so the field at the centre of C is

The field at the centre of C is T.

JEE Main · 2021 · 18 Mar 2021 · Shift 1 · Single correct option

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