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JEE Main201912 Jan 2019Morning ShiftPhysicsMagnetic Effects of CurrentActual

As shown in the figure, two infinitely long, identical wires are bent by 90 o and placed in such a way that the segments L P and Q M are along the x - axis, while segments P S and Q N are parallel to the y - axis. If O P = O Q = 4 c m , and the magnitude of the magnetic field at O is 10 - 4 T , and the two wires carry equal currents (see figure), the magnitude of the current in each wire and the direction of the magn

Options

  1. A20 A , perpendicular into the page
  2. B20 A , perpendicular out of the page
  3. C40 A , perpendicualr into the page
  4. D40 A , perpendicular out of the page

Correct answer

A. 20 A , perpendicular into the page

Step-by-step solution

As we know that the magnetic field due to a infinite wire at a distance of d is given as B = μ 0 i 4 π d but there are two wires so that the net magnetic field is given as B = 2 μ 0 i 4 π d 10 - 4 = 2 4 π × 10 - 7 × i 4 π × 4 100 i = 20 A

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